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Posted: 8/10/2007 8:42:02 PM EDT
[Last Edit: ar-jedi]
PLEASE DON'T POST REPLIES IN THIS THREAD!!! folks, if you have a specific question or concern about the thread, just IM me. thanks much. ar-jedi ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––-
ham radio 101
Originally buried on page 4 of this thread, here it is in it's entirety + more info for new folks to read through. Please note that this thread is for the most part a compendium of my prior ham-related posts AND informational posts from a number of fellow ARFCOM SF members. I have attempted as best as i could to preserve the original attributions, but if I missed some authors I assure you it was not intentional. Drop me an IM and I will correct the oversight immediately. 
Here is a start at a soup to nuts ham primer... I'll take a shot at this, and provide some links as well since my fingers would fall off before I could type everything you might want to know. The usable-for-communications electromagnetic spectrum spans a frequency range from about 100KHz to 100GHz. (Aside, only a portion of that is usable by inexpensive equipment). In the USA, the Federal Communications Commission (FCC) is responsible for administering the spectrum for US users; however, the FCC works closely on this with international bodies, for reasons which will soon become clear. The "administering" that the FCC performs includes dictating what frequency bands are to be used for what purposes, and also specifying operational requirements for those bands (e.g. TX power output, ERP, modulation type, etc). Since examples are worth thousands of words, I'll provide a few... 1) the FCC has decided that broadcast FM music stations are to exist in the 88MHz to 108MHz range, with maximum power limits. 2) the FCC has decided that CB exists at around 27MHz, and that the maximum TX power output is 4W. 3) the FCC has decided that FRS exists around 462/467MHz, with a maximum ERP specified. And for the last example, 4) ham (amateur radio) has a number of bands allocated, each with associated limitations on power/modulation type etc. I could go on and on with cell phones, marine radios, garage door openers, keyfobs, microwave towers, etc etc etc. Basically, if the device is what is referred to by the FCC as an "intentional radiator", they have an assigned slot (band) for it and constraints on it's operation. Why the constraints? Well, one reason is for your physiological protection. High RF power can cause burns, blindness, and other problems. (The "invention" of the microwave oven was an accident –– technicians working on early radar antennas were developing burns when the units were powered). Another reason for the constraints is public safety. The last thing a 747 pilot on emergency approach into Kennedy airport needs is crosstalk with taxi dispatchers in NYC. Hence the wide berth the FCC gives around police, fire, and EMS frequencies. Now then, we see that the FCC regulates intentional radiator use by dividing the frequency spectrum into bands, and then sets characteristics for each of those bands that users must obey by. A common question is, "is one frequency band 'better' than another"? The answer is "sometimes". For certain applications (more on this in a moment), a given frequency band may provide better range, fidelity, immunity to interference, and so forth. These factors, and others, that make a frequency usable for a given application were taken into consideration when the spectrum was allocated. It is important to note here that transmitter power output is one of many, many factors that influence the range at which you can communicate over a given transmission path. While important, transmitter power output plays only one role in a multi-faceted problem. Antenna gain, antenna polarization, modulation type, receiver sensitivity, background noise level, path loss, and a dozen other issues factor into the equation. Show me a well designed 2W transmitter and I will show you a way to communicate ~6.5 billion miles. NASA does this every day with their Voyager 1 & 2 probes –– they are now twice as far away as Pluto. Now that you understand a little of the background of radio communications, we can move on to discussing amateur (ham) radio specifically. To simplify things, amateur radio communication can be thought of in two segments: HF and VHF/UHF. First, i hate to break this to you, but THE EARTH IS ROUND. No, I'm not kidding –– it really is spherical despite what they told you in school or at church. Ok, now that you are past that, you should visualize in your head that radio waves travel in a straight line. Since the earth curves, it is not possible to talk over distances of over about 20 miles without "help". This "help" can come in a multitude of ways, and is somewhat dependent on the height of the transmitter and receiver, the gain of their respective antennae, the frequency of transmission, the weather and other atmospheric conditions, the sun cycle, hams around you erecting things called repeaters, and a few dozen other things. Nevertheless, the key point here is that the further you are away from each other, the more likely it is that the curvature of the earth is going to be the limiting factor. Always remember that without "help", radio communications of any type are "line of sight". HF, or high frequency (roughly defined as everything below about 30MHz [10 meters wavelength]) signals can bounce off of a charged belt (called the ionosphere) which completely envelopes the earth. HF thus can communicate over long distances by using one or more "bounces" –– you may have heard the CB term "skip". With just a few dozen watts, and a proper antenna, it's possible for you to talk (or more likely communicate using morse code) with a station 2000 miles away. Interestingly, it is sometimes difficult to talk to nearby stations that are "under the skip", that is they are too close to you to hear the reflected wave. One primary disadvantage of HF communications is that the antenna has to be physically long. Nevertheless, HF can be a valuable asset in emergency commications –– like it was during hurricane Katrina when everything else was tits up. In general, when you think of HF you should think of long distance communications. With some exceptions, most HF rigs are designed for desktop use and the supporting equipment (power supplies, antenna tuner, etc) is heavy and not so portable. But there is a class of mobile and low power HF rigs which allow you to talk over great distances with just a few pounds of equipment. Aside: there is an entire "sub-culture" within ham radio of people dedicated to QRP, or long distance very low power communications. Hundreds or thousands of miles on 5W, 1W, or even 0.5W is their goal. Antenna selection and a very good idea of what the ionosphere is doing are prerequisites. VHF/UHF, or very/ultra high frequency (roughly defined as everything above about 50MHz [6 meters wavelength]) signals do not bounce off of the ionosphere. Hence, VHF/UHF is pretty much "line of sight" except for some atmospheric effects which occasionally allow communications to take place out to a few hundred miles. These effects can not be "scheduled" though, mother nature has her own clock. In other words you can not depend on these phenomena for reliable communications. When you think of VHF/UHF you should think of short distance comms. Amateur radios in the 6M (50MHz), 2M, (146MHz), 1.25M (220MHz), and 70cm (440MHz) bands are examples of VHF/UHF equipment. Hand held radios in these bands are knowns as "HT's", or handy talkies. Of course there are mobile and base versions as well that sport more output power or additional capabilities. Since a picture is worth 1000 words: 
Continuing on, FRS (UHF, ~462/467MHZ) and GMRS (UHF, same) are examples of inexpensive general purpose you-don't-need-a-ham-license radios. Most commercial radios (tow trucks, florists, plumbers, Amtrak, mall ninjas, etc) operate in the 150MHz VHF band. And until somewhat recently, most public safety (police, fire, first aid) were in the 150MHz and 450MHz bands as well. However, within the last 5 years many have migrated to the 900MHz band using what are called trunked radio systems. long story there but trunking allows a lot of flexibility for the system. You'll note that VHF/UHF radios are cheap, small, have short antennas, and long battery life. Moreover, amateur VHF/UHF radios double as scanners for the public service and other frequencies as well. The most popular VHF/UHF "band" is 2M, or about 146MHz. There is a reason for this... read on... an introduction to VHF/UHF repeaters As noted above, the primary limitation of VHF/UHF is the short range imposed by the curvature of the earth combined with the fact that VHF/UHF signals do not bounce off of the ionosphere (in case you were wondering, they pass right through it). Of course it helps greatly with VHF/UHF to be up as high as possible, as this gives more "line of sight" distance –– the same way you can see much farther when atop a tall building. But that's not always practical. e.g., I live right at sea level –– no kidding. So how can I communicate with any distance using VHF or UHF? Am i stuck trying to use HF for communications more than a few miles? Enter the "repeater". Simply put, a repeater is an unattended radio advantageously located on a hill or with the antenna high up on a tower. The purpose of the repeater is to retransmit your signal in real time. It does this by listening on one frequency, called the input, and simultaneously transmitting the input audio on a second frequency, called the output. Accordingly, my radio would be set to transmit on the repeater's input frequency, and listen on the repeater's output frequency. (The difference is known as the "offset".) All that is required from a radio implementation standpoint is a little bit of frequency agility –– when you press the transmit button, your radio tunes it's transmitter to the required new frequency. When you unkey, it changes back. All this happens in milliseconds and without your involvement save for some initial settings. The beauty of this set up is that with a low power HT (typically, 0.5W to 5W) you can talk for perhaps hundreds of miles! The repeater provides the "help" for VHF and UHF, just like the ionosphere provided the "help" for HF. Ham radio clubs set up, operate, and maintain repeaters. There are likely several repeaters reachable from where ever you are reading this from. From my home I can reach about 8 repeaters, of course I do live near a metro area with a high population density. Note that there are published books of public amateur repeaters, which denote their location and characteristics (e.g., output frequency and offset). The reason that 2M/146MHz radios are so popular and inexpensive is simply due to the fact that there are more repeaters on 2M than any other frequency. Note: don't think that repeater technology is something specific to hams –– it's not. Police departments and the like use repeaters for the same reasons that hams do. In fact, this created a big problem on sept 11, 2001 as several of the NYPD and FDNY repeaters were located atop the WTC. The disadvantage of repeaters is simple: in order for the repeater to work, you need power and the antenna has to be upright. These are not likely conditions in areas overcome by, for example, a category 4 or 5 hurricane. While tons of lead acid batteries may delay the inevitable, there is a finite amount of no-AC-power operation time for any repeater unless expensive measures have been taken (e.g. a diesel genset and good sized fuel tank, as you would find mounted behind a police station). Nevertheless, hams are resourceful people and generally fixing the local repeaters is an immediate priority in disaster areas. Moreover, all of the equipment necessary for a repeater can be carried in the back of a pickup truck, with room to spare. So if a makeshift antenna can be erected on the mountainside, a substitute repeater can be up and running in a few hours to replace the one crushed by the flying oak tree. One way to look at a ham repeater is as an analog of a cell site. Having many cell sites make it possible for your low power cellphone to communicate anywhere the global phone network reaches. Similarly, hams link repeaters using point-to-point RF, the phone network, or these days using the Internet. All of these methods allow greater "reach" from your low power HT. Of course with the exception of point-to-point RF, the other methods require public infrastructure that may or may not be available when the SHTF. Speaking of the Internet, I've discussed above mainly voice communications. However, hams also have packet radio technology at their disposal. So email and traffic nets can be set up without relying on the Internet –– instead of wire and fiber, RF is substituted. Think of it as a wireless LAN, capable being accessed by anyone in an area of a few dozen miles in diameter. In short, ham radio is not a singular thing; it is a wide, expansive hobby with many aspects to it –– you simply choose the parts that you enjoy. It's no different than with trucks, some like lifting and then offroading their trucks, and others make lowrider bling-bling trucks out of them. Similarly, hams do HF, VHF, UHF, microwave, CW, packet, APRS, DXCC, contesting, SSTV, fox hunting, RACES/ARES, and so on and so forth. |
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Posted: 8/10/2007 8:42:34 PM EDT
[Last Edit: ar-jedi]
[#1]
how to get a ham radio license, in short Can you get the License online?
No. There are three levels, called "classes", of amateur radio (ham) licenses, which give increasing privileges on the bands assigned by the FCC for exclusive use by amateur radio. None of the license classes require learning Morse code, but they all require taking a written exam given by volunteer amateur radio operators in your area. The steps to get the base license, called a Technician (abbr. "Tech") class license, are like so... (1) Go here: http://www.hello-radio.org/ there you will find out more about amateur radio and the multitude of facets to the hobby. (2) Get a Technician class study guide. you may be able to get one for free (or near so) from one of the folks here who have recently earned their Tech license (it's a pay-it-forward kind of thing). you will need to read through the Tech study guide over the course of a few evenings. you can also find a lot of info on the web to help study for the Tech exam ––> link (3) Take the practice exams located at http://www.qrz.com/hamtest/. repeatedly take the Tech exam until (a) you have seen all of the questions in the question pool (the question pools are public, and located here), and (b) you get a passing score every time. it is certainly possible to memorize all of the answers to all of the questions, but i dissuade you from doing so as you'll need some of that knowledge down the road. (4) Go here http://www.arrl.org/exam_sessions/search and put your zipcode in. This locates a nearby VE (volunteer examiner) session. The exam session itself will likely be located in a school classroom, a library, or similar civic building. In some areas they may be as often as every other week. In some areas they may be once a month. You'll bring a pencil, some government issued ID like your driver's license, and $15. You can take the Tech exam in about 15-20 minutes, and you are a ham. Note that there is no additional charge to take higher class exams on the same day; hence, if you want you can study for both the Tech and General exams, and take them both. The General class license gives a ton more operating privileges than the Tech class license, and is especially needed for long distance (>50 miles) communications. I highly recommend studying for both your Tech and General licenses and taking them both in one sitting. (5) About a week after you pass your exam, a letter will arrive from the FCC with your assigned amateur radio callsign. Congratulations! See also, www.arrl.org/FandES/ead/classes.html and http://www.arrl.org/what-to-bring-to-an-exam-session how much are they?
As demonstrated above, you can't "buy one", per se. It's ~$15 for the exam session –– see link above –– but you can take tests sequentially at the session if you want, all for the same cost. ––- My question: is morse code required for any of the licenses any more?
No, not since February 2007 –– it is not required for any class license. reason i ask i know you have to walk before you can crawl, but if i wanted to get the general or the extra license would morse code be required ? also at what level do they require morse code to be learned?
Per above, you can learn morse code on your own volition, or not. It is not a requirement for licensing. This, by the way, is not a uni-lateral move by the FCC (the USA's spectrum authority). The ITU, a committee which helps regulate and harmonize international spectrum use, recommended in 2006 to it's member countries (basically everyone) that morse code be dropped as a requirement for amateur radio licensing. Several countries did so immediately; naturally it took us longer to wind the rule change through our bureaucracy. But here we are –– no more Morse code requirement for licensing. By the way, that does not mean Morse code has "gone away" from a usage perspective. For example, go listen at the bottom of the 40meter band (day or night) and you will hear dozens of Morse code conversations (called QSO's) in progress, from all over the world. CW (Morse code) is a remarkably efficient mode, and can be used for communications when there is no way to get the spoken word through. With the new knowledge that Morse is no longer needed. I plan to go out and buy some study aids immediately and start studying... Seems like as you have said the best bang for the buck is the General. That will be my goal in the not too distant future.
Yes, with the General class license you get 99% of the privileges you'll ever need. The Extra class license gives you additional slices of the HF bands. Again, I'd suggest studying for the Tech and General concurrently –– you can pass them both in the same day in under an hour, and one $15 test fee covers them both. now i have to get study materials.
Suggestions –– (a) Post that you need a Tech/General study guide in the ham radio forum. Someone will send you slightly used one for a couple of bucks. It's a "pay-it-forward" thing with hams. (b) Find a local club and drop in on their monthly meeting. There are no scary animal acts or anything like that, LoL. You'll find a good bunch of guys/gals. The folks in the club probably are the same folks giving the exams and they will go out of their way to help you out. ––- On-line study guides: LINK UPDATED FOR NEW 2010 TECH QUESTION POOL: http://www.kb6nu.com/wp-content/uploads/2010/06/2010_Tech_Study_Guide.pdf LINK UPDATED FOR NEW 2011 GENERAL QUESTION POOL: http://kb6nu.com/wp-content/uploads/2007/09/2011-No-Nonsense-General-Class-License-Study-Guide.pdf For more information on the above guides, and/or to order printed or Kindle/Nook versions, see http://kb6nu.com/tech-manual/ –––– Meanwhile, I'm going to keep up on the Tech questions and try to bring the General scores up to a more comfortable margin... well, really, I don't want to just scrape by. I want to actually learn the material.
WARNING THIS IS THE OLD 2006 TECH QUESTION POOL –– NO LONGER VALID! abacus.nmsu.edu/~shoran/PDF/Tech_Course.pdf WARNING THIS IS THE OLD 2007 GENERAL QUESTION POOL –– NO LONGER VALID! abacus.nmsu.edu/~shoran/PDF/General_Course.pdf I have just started today gathering up info for the Extra exam.
use this ––> abacus.nmsu.edu/~shoran/PDF/Extra_Course.pdf –––– Originally Posted By JaxShooter:
In addition to just reading the question pool, here are some sites you can try for practice exams: AA9PW eHam And probably my favorite, RadioExam I like RadioExam because you can narrow it down to a particular section. That way you can focus on your problem areas rather than taking complete tests. This is especially valuable for the Extra exam since it's 50 questions. –––– Originally Posted By JaxShooter:
Originally Posted By ar-jedi:
dear VE, what kind of facility do you administer the test at? Our club uses a meeting room at one of the local malls. I have also conducted sessions at a branch library for another club. how much does the test session cost? The ARRL VEC Exam Fee for 2011 is $15.00. W5YI's current fee is $14.00. Volunteer examiners are permitted to charge a fee to recover their out-of-pocket costs in administering an examination so it's possible for this amount to vary slightly. how long does a typical technician test take to complete? This depends on you. I've seen people ace it in about 15 min while others take 30-45 depending on their confidence level and the time they spend re-checking their answers. If there are a lot of people testing your longest wait may be in getting your exam graded. Each exam is graded by all three examiners. Multiply that by the number of people testing and figure 10 min or so for us to fill out all of the paperwork. can i take more than one test at a single sitting? If you fail the exam you can retake it after paying the fee again. This may be time dependent, though. For example, our location closes at 9pm and we have to be out before that so we may not have time to administer another exam. assuming i pass the technician test, does taking the general test cost extra? Following on with the previous question, when you pass your exam you can take the next exam at no cost. As long as you keep passing you can keep testing for the cost of the single exam fee. It's possible to go from zero to hero and get your Extra for one fee if you pass Tech and General together. If you feel confident about your Technician and think you may like to try General, please let the VE team know ahead of time (especially if you pre-register). This allows the team to have your paperwork and multiple exams in order. can i skip taking the technician exam and just go right to general? No what happens after i pass –– you send the results somewhere and then what? When you pass your Technician exam you will be given a CSCE that says you passed. The VE team will then take all of your paperwork and send it (either via USPS, FedEx/UPS, or electronically) to the VEC. Once they have your paperwork it will be transmitted to the FCC so your call sign can be assigned. Since you do not have a license yet cannot transmit. Typically within a week your call should show up in the FCC ULS database. Once your call appears you can get on the air. You don't have to wait for the paper license to appear in the mail. If you are upgrading your license you can start using your new privileges once you walk out the door with your CSCE as long as you use the appropriate designator for General (/AG) or Extra (/AE). –––– useful/interesting amateur radio sites www.eham.net www.qrz.com www.dxzone.com www.arrl.org www.qrz.com/i/howtoham.html <<<*** www.qrz.com/p/testing.pl <<< *** wireless.fcc.gov/services/amateur/ www.ew.usna.edu/~bruninga/aprs.html RACES/ARES www.ares.org/ www.races.net/ Originally Posted By GlockTiger:
Cool link I found For all the guys new to HF, this is a great primer! ps: As a side note: But now I think a ham is the way to go
Like firearms, ham radios come in lots of different sizes and shapes, and are suited for different purposes. You can't go elephant hunting with a .22LR, and similarly you won't have much to eat if you go squirrel hunting with a .50 BMG. What i'm getting at here is that you first need to define what you want to do, and then figure out what kind of ham radio you are looking for. Some are multi-purpose, and cover 90% of what you'll ever need to do. However, a good setup requires as much attention to the antenna system as the actual radio. It is quite easy to get poor results with an expensive radio and a crappy antenna. It's no different than trying to corner quickly in a Ferrari equipped with junk tires. but how much are they?
See above. It could be $100 to $2000 for the radio, and $0 to $1000 for the antenna system. Few folks will need a $2000 radio and a $1000 antenna, unless they are really into the hobby. But I've noticed that a few folks who are really into guns buy Accuracy International rifles at ~$5K each as well, and then mount a $2K optic on top. |
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Posted: 8/10/2007 8:43:08 PM EDT
[Last Edit: ar-jedi]
[#2]
simplex communications and approximate ranges For mobile to mobile communications, such as would occur when off-roading, you can use "simplex" (direct) communcations in the VHF 2 meter band. No repeater needed, you are talking directly to each other. A common frequency for initiating this is 146.52MHz, the national simplex calling frequency. Once you have contact made you can move up a few hundred kilohertz and use any of the designated simplex frequencies to carry on. Using an HT (handie-talkie) running 1 to 5W, you can expect up to about 5 miles of range. It depends highly on the terrain (flatter better) and what sort of antenna you have connected. Using a mobile rig running about 50W into a roof or bracket mounted antenna will net you anywhere from 10-50 miles of range. Generally the curvature of the earth will cause problems, so it is better to be up on a hill of you are trying to reach out past 20 miles or so. A 2M-only HT is about $130-150. A 2M-only mobile is about $140-180. Many HT's and mobiles are "dual-band" in that they operate on both 2M (~146MHz) and 70cm (~440MHz). This gives more flexibility for operating. note however there are far far far more repeaters on 2M, so there is no significant downside to getting a 2M-only rig. However, some public service agencies use frequencies in the 460MHz range, which a 2M-only radio will not be able to receive. Popular HTs and mobiles come from the Big Three: Icom, Yaesu, and Kenwood all make fine radios with marginal differences. Mostly it's individual preference, unless one feature is striking you just right. The Icom V8000 is a very nice 2M-only 75W mobile rig. I happen to own two of them. As for HT's, there are also many types; I own a Yaesu VX6R -- tri-band (incls 220MHz) super small and completely waterproof. I also own an Icom 24AT, a rugged dual-bander which I have had since 1991. It has never let me down and i've worked through a few Nor'Easters and hurricanes with it. www.yaesu.com/ www.icomamerica.com/ www.kenwood.net/ One thing i just realized, i never really explained what modulation is. Simply put modulation describes the technique used to put the audio input to the radio (i.e. your voice) onto the RF carrier. There are many ways to do this, each with advantages and disadvantages. Moreover, not only can it be done in the analog domain, but it can be done digitally as well. I'll only discuss the former as there are very few consumer digital radios to be had. The most common analog modes are CW (continuous wave), AM (amplitude modulation), FM (frequency modulation), and SSB (single sideband [suppressed carrier]) modulation. CW is used for morse code and is very efficient for long range comms. CW is not really a modulation method per se, but nevertheless we treat it as such. AM, as you may be aware, is used for broadcast radio stations (hence the "AM band" name) and for shortwave stations (like Voice of America and Radio Free Europe). Because of the low fidelity of AM, and it's susceptibility to interference, AM radio has been relegated mainly to talk and newscasts. Note that CB uses AM as well. FM, as you are also aware, is used for broadcast radio stations and also is the mainstay for VHF/UHF communications. Above 50MHz (6M), 99% of ham, all of FRS/GMRS, marine, and all public service/safety use frequency modulation. FM provides far greater fidelity (accuracy of the receiving radio's output to the transmitting radio's input) than any other modulation type. Therefore, FM is very useful for music transmission. And similarly, FM makes 2 way radio communications crystal clear. Most folks who have only used a CB are incredulous at what a 2M ham rig sounds like. the difference is due to the use of FM -- and not power or anything else. In addition, FM is all but immune to atmospheric disturbances such as lightning. SSB is the most complicated of all of the noted modulation techniques. Simply put, SSB is an adaptation of AM with a little math (a Hilbert transform) thrown in. The result is a VERY efficient way to transmit speech over long distances. SSB is the primary modulation method used by hams when operating below 50MHz (6M). There are actually two variants of SSB (USB and LSB) and in order to communicate both parties need to use the same type. Nevertheless, SSB is one reason you can talk a few thousand miles on a couple of watts. --- 
SSB is one type of "modulation" -- which is an expensive word to describe the process that radio uses to get your voice encoded onto a radio signal. You have heard of AM, FM, and so on, these are modulation methods as well. SSB is uniquely suited for long distance work as it is extremely power efficient, has a narrow spectral bandwidth, and a very weak SSB signal can easily be recovered by the receiver at the other end. SSB does suffer in terms of fidelity, that is trueness of sound to the original source; SSB is also more prone to noise from atmospheric disturbances such as lightning. The clear winner for fidelity is FM, which is why FM is used to broadcast music. But FM requires a wide swath of a given band. AM is not so great in *any* department -- it is prone to interference, has poor fidelity, and the spectral efficiency is mediocre. Nevertheless, the design complexity of both an AM transmitter and the corresponding AM receiver is very low, and therefore overall "system" cost is very low. A basic AM receiver can in fact be constructed from a single diode and in some case requires no external power. This is not the situation with FM or SSB. Amateur (ham) radios designed for high frequency (HF =~ 1Mhz [300m] to 30MHz [10m])) operation have a selector switch which allows the operator to select the modulation type, choosing from AM, FM, SSB (USB or LSB), and finally CW (for sending morse code). By convention, international agreement, or other reasons, certain radio frequencies (aka bands) use certain types of modulation. For example, the BBC World Service shortwave stations transmit in AM. But the US Coast Guard rescue HF frequencies use SSB. Now then, I've talked about the various modulation methods such as AM, FM, and SSB. Frequency comes into play because the "skip" effect you referred to is wholly dependent on the whims of the ionosphere (a region high up in our atmosphere). The "reflectivity", if you will, of the ionosphere is a function of many things, including high energy particle emissions from our sun. To sum up, depending on conditions, at a given frequency, you can can get excellent skip, marginal skip, or no skip. And, for a given time and place, there is a maximum frequency for which there will be no skip whatsoever -- this is known as the MUF -- maximum usable frequency.  The basic problem with skip communications is it doesn't help for the area "under" the skip. In other words, with skip you can sometimes talk to Europe from New York, but you can't talk to NJ. Because of this issue, generally a different approach for "medium range" comms. Hence, i think you are going to have some trouble with your proposed usage of 10m SSB, for a couple of reasons. Keep reading... For the distances you are looking at, 60 to 100 miles, IMHO you really have two choices: (1) Use 6m or 2m SSB, decent amplification (typ 200-400w), and high mounted, highly directional antennas (e.g. 4 to 12 element horizontally polarized yagis). This is basic "line of sight" communications -- no fancy skip here. A few folks near me clear 100 miles using this approach all of the time. Note that maximizing antenna height at both ends is critical! If the antennas can "see" each other, without a hill or mountain in the way, you'll have good comms. (2) Use 80m or 40m SSB, normal power (typ 100w), and a NVIS antenna setup. With NVIS, which is an acronym for "near vertical incidence skywave", your transmitted signal is more or less directed straight up -- the resultant reflected wave will cover the surrounding few hundred miles. The military uses this approach for HF communications in tactical (battlefield) applications (although less so these days with so many milsats overhead). My fingers will fall off before i can type all that is possible to describe NVIS in details, hence I suggest reading the following... en.wikipedia.org/wiki/Near_Vertical_Incidence_Skywave www.qsl.net/wb5ude/nvis/index.html www.w0ipl.net/ECom/NVIS/nvis.htm www.tactical-link.com/field_deployed_nvis.htm To quote from the first link above, which sums things up nicely:
ps: Note that SSB can be done two ways: upper side band (USB) and lower side band (LSB). While SSB (single side band) describes the general modulation concept, the receiver operator must actually select either USB or LSB in order to correctly hear the signal. |
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Posted: 8/10/2007 8:43:43 PM EDT
[Last Edit: ar-jedi]
[#3]
Since someone is bound to ask... what does 2M mean? Why is it seemingly used interchangably with 146MHz? Hams simultaneously use one of two terms to describe the band they are discussing: frequency or wavelength. The two are related by a constant known as C, the speed of light. It turns out that after you crunch the numbers, you can easily convert between the two terms using the following rule of thumb... 300/freq in MHz = wavelength in meters or the same rule but turned around, 300/wavelength in meters = freq in MHz hence: 300/146MHz ~= 2 meters and now you see why 146MHz and 2M are used interchangably. Simlarly, some wavelength to frequency conversions for other popular HF and VHF/UHF ham bands... 40M --> 300/40 ~=7.5MHz 20M --> 300/20 ~= 15MHz 10M --> 300/10 ~= 30MHz 6M --> 300/6 ~= 50MHz 1.25M --> 300/1.25 ~= 220MHz 70cm --> 300/0.70 ~=440MHz Other cool/random radio-related links... wiki stuff of interest: en.wikipedia.org/wiki/Amateur_radio en.wikipedia.org/wiki/High_frequency en.wikipedia.org/wiki/20_meters en.wikipedia.org/wiki/Very_high_frequency en.wikipedia.org/wiki/2_meters ham radio bandplan: www.arrl.org/FandES/field/regulations/bandplan.html |
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Posted: 8/10/2007 8:44:19 PM EDT
[Last Edit: ar-jedi]
[#4]
general ham topics Q & A
Yes, CB exists within the "HF" frequency range (~1MHz to 30MHz), as does amateur radio. CB is allocated, as you already know, a band right near 27MHz (~26.965 to ~27.405), and the amateur 10meter band is just slightly higher at around 28.0 - 29.7 MHz. All things being equal, a CB and and a 10m ham radio would have approximately the same range since they are both affected the same way by the ionosphere. But clearly there is something else different, something that gives one an advantage over the other... keep reading...
Power is one aspect of range, an important one -- but not the only one. As I discussed in the third or fourth post in my "Ham 101" thread, the way the audio is modulated onto the RF carrier is extremely influential on how easy or difficult it is to recover the audio at the other end. AM is one of the worst possible ways to transmit voice, and that's the type of modulation CB uses. AM, combined with only 4 watts output, is just not going to make it as far as a superior modulation method combined with more power. In contrast with AM, SSB is much much much (i can't emphasize this enough!) more efficient in terms of using the available power to greatest effect. Ergo, SSB, combined with the higher power available on ham rigs, allows for far greater communication distance at very nearly the same frequency as CB. So as you can see, it's not just about power. (I would also like to point out here that the receiver section on a typical ham radio is miles ahead of the receiver section on a typical CB radio. You need to cut some pretty big corners in order to make a CB that sells for $50. A ham rig, on the other hand, is at a price point that allows for better components (oscillators, filters etc) and additional circuitry (especially DSP [digital signal processing]). If you look at the entire communications path from strictly a power perspective, there are two factors: how powerful the transmitter is and how sensitive the receiver is. Hence, you can improve range by increasing transmitter power and/or increasing receiver sensitivity. If you do both, you get a lot more range. This is the case with the higher power output and excellent receivers on ham radios. And we haven't even plugged in the benefit of using SSB modulation yet! remember, IT'S NOT JUST ABOUT POWER. Lots of hams use less than 10W to talk around the world. The art here is understanding propogation conditions, using the right modulation mode, driving a proper antenna, and having a good quiet (low noise floor) receiver.
The ionosphere does not reflect frequencies above about 30MHz. Above that, they just keep on going, off towards Mars. So, unless under very infrequent conditions, 2M (~146MHz) can not be used for long distance comms as it will not bounce back down to earth. (Aside: there is a aspect of ham radio which consists of bouncing 2M signals off of the moon. This is called "EME", or "earth-moon-earth" communications. In this manner you can use 2M/144MHz to talk to the other side of the earth. Warning: you need a lot of power and a big ass beam antenna array to pull this off. Moreover, the antenna must be able to track the moon as it crosses the sky, guided either by optical means or by using ephemeris data)
You can use the "national simplex frequency", 146.52 sort of like CB channel 19. My 2M radio is set up to scan it in one of the memory banks. Often i will hear someone call on it, and answer back. Sometimes they are just trying a new radio out, other times they are from out of town and looking for popular local repeater frequencies, and other times it's just to say "hi" and so forth. Generally you can "meet up" on .52 and then move off slightly to allow others to use the calling frequency. Or you can simply chat on .52, allowing a little extra time between alternating transmissions -- then if someone wants in, they will interject with just their callsign. At that point you will "recognize them" by repeating their call back and saying "go ahead" (in effect, handing them the baton for the moment), and thus allowing them the opportunity to either join your conversation or to call for another station that they may have had a prearranged hook-up time for. This is actually all very simple and the first time you hear it happen live it will be very clear to you how to do it yourself in the future. The operating procedures in place on ham radio make it a much more enjoyable environment for everyone.
That is correct. Pass the Technician class written test (no morse code test required) and will you have full operating privileges over 50MHz (6 meters). Your FCC callsign will arrive in the mail in about a week, and you are a ham. Borrow/buy a 2M radio, and you can chat with the nearby hams on 146.52 and of course use the local repeaters as well. For any new ham I would suggest listening to conversations (called "QSO's") on the repeaters for a bit to get the operating procedure down. Again, it's VERY simple but you should listen first to see how it's done before jumping in with both feet.
You absolutely need a license to operate HF! You only need to pass the General or Extra written test in order to operate HF (again, no morse code test). The morse code requirement went away in February 2007 away, as the ITU (International Telecommunications Union, sort of like a "global FCC") and many countries have already done away with it.
Oh, maybe you have a basic misunderstanding about something -- hams don't own ALL the spectrum above 50MHz!!! Hams have been allocated tiny little chunks, that's all. Other chunks are used for hundreds of other purposes, including police, EMS, fire, military, coast guard/marine, national park service, business band radios, taxis, aircraft, cellphones, NASA, and so on. Even your garage door opener has it's own band, as does the 802.11 wireless router you probably have at home. Things you don't even think about, like the little RFID tags used to prevent shoplifting, have their own bands. Along those lines, the FRS (family radio services) and GMRS (general mobile radio services) have bands allocated in the 462/467MHz range. These are "the new CB's" -- walkie talkies sold in pairs EVERYWHERE (walmart, sears, you name it) and seen at amusement parks, ballgames, and soccer fields, etc so kids can stay in touch with their parents, hunters in a group can talk to each other, and so on. Power limited and with fixed antenna sizes, they are channelized like a CB to keep operation simple. "mom, i'll be on channel 2, mmm-kay?" is all it takes. FRS, no license required. GMRS, you just need to send the FCC a filled out form and $50(?) to get a 5 year "family license" or something like that. Due to power limitations, there is no such thing as an FRS mobile radio, so you are limited to the little walkie talkies and about 2 miles range (approx). No FRS repeaters either to help things. So an FRS radio is not a substitute for a ham radio in all cases. You can't get the same range simplex nor can you utilize repeaters for even more range. On the other hand, FRS radios are dirt cheap, and if you are in a caravan of cars they sure are handy to use to talk between them. |
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Posted: 8/10/2007 8:54:28 PM EDT
[Last Edit: ar-jedi]
[#5]
setting up a station at home using a mobile radio
I'm going to assume that you are trying to take a VHF (2m) or VHF/UHF (2m/70cm) mobile radio and use it at home as a base. RADIO The radio itself will come with a microphone, an unterminated DC power cable, a mounting bracket, and a variety of screws. On the back of the radio is an antenna connector, which for these rigs is typically the UHF/SO239 type. AC->DC POWER SUPPLY A 50W VHF/UHF mobile will need approximately 10-12A at 12Vdc for full output. There are two types of AC->DC power supplies: the tried-and-true linear regulated power supply and the newer type called a switch-mode power supply (sometimes abbreviated SMPS). The linear regulated power supply uses a large transformer and large capacitors, hence it is bulky and heavy for a given current output. They also can run hot. one advantage however is that it is "quiet" electrically -- that is, this design produces very little to no RF "hash" which can sometimes interfere with weak signal work. The switch-mode power supply uses a much more compact design, and is lighter, but can be more "noisy" from an electrical perspective. Newer switch-mode power supplies have largely tackled the RF noise issues, and in any case these noise issues affect HF operations to a greater extent than VHF/UHF operations. For this reason I suggest getting a good SMPS like the SAMLEX 1223. This 23A output model is very well regarded and costs about $99 at the various ham outlets. Shipping is inexpensive since it weighs about 3 lbs. Contrast this light weight with a comparable output linear regulated power supply. BATTERY POWER In addition to using the AC mains for input power, you will want to investigate using a battery for backup, and also integrate some method of recharging the battery. There are a lot of options here. One is to get a sealed gel/cell (aka AGM) battery and use a small charger called a "Battery Tender Jr" to keep it topped off. When the AC fails, simply connect your radio to the battery and you are back in business. A second method is to use a device called a Powergate to simultaneously hook up your radio to a battery and a power supply. The Powergate will keep the battery charged and instantly switch over from the AC->DC power supply input to the battery if the AC mains fail. ANTENNA COAX Depending on the length of the run, you can use one of two types of coax: RG58 (approx 0.250" in dia) or RG8 (approx 0.400" in dia). All things being equal, the larger diameter coax will have less loss; this means more of your transmitter power gets to the antenna, and your receiver hears better as well. For runs under 50', i think you'll do OK with the less expensive RG58 type. Over 100', I'd consider RG8 a necessity. Notice that these two generic types come "branded" by different manufacturer's somewhat differently. Nevertheless, find and study a coax cable loss table with an eye towards 150 and 440MHz; see for example www.hamuniverse.com/coaxdata.html. There are a number of high quality low loss coax types from manufacturers such as Belden, Andrew, and Times-Microwave. Times LMR400 (RG8 type) is especially popular, as is Belden 9913F7. ANTENNA CONNECTORS You will need good quality PL259 connectors for both ends of the coax. Avoid the Radio Shack plated crap. AMP and Amphenol make quality connectors. ANTENNA My recommendation is to get a quality dual band fiberglass antenna, such as a model from Diamond or Comet. I have a very "low profile" 6 foot high Diamond X50 on my house and it works fantastic. You can get more gain with longer antennas but you may get more questions from your homeowner's association as well. YMMV here. You want the antenna as high up as possible, with no structure within about 10 feet of the vertical element. |
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Posted: 8/10/2007 9:02:35 PM EDT
[Last Edit: ar-jedi]
[#6]
using a repeater, part I
I think that you have already figured it out ... listen for a bit to how it works.
Ok, i'm going to make some assumptions here; namely, you know the repeater input and output frequencies differ by (typ.) 600Khz (0.6MHz), and you know that the repeater may employ a PL tone on the input, and finally you know how to set your radio to use the correct offset and PL tone. You can test this by making a short TX while no one is using the repeater. Some call this "kerchunking" the repeater. Set up your radio, press the PTT button for about 3 seconds, and release. Immediately you should hear the repeater output (strong signal but no audio), then the courtesy beep, and then the repeater signal will go away. Make sure you can get this far. If you have to do additional testing, simply repeat but add "this is <your callsign>, testing only" to your transmission. Note that if you don't press the PTT long enough (say for only one second), the repeater may not come up. This is a desired feature, so that any short-lived RF noise does not inadvertently activate the repeater. --- As opposed to, say CB, using a repeater requires following some specific operating procedures. This is done to ensure that everyone has access to the repeater, and higher priority (for example, emergency) communications can have precedence over daily chit-chat. Let me give you an overview of the common, daily repeater operations. In general, if the repeater is not "in use", you can thow a stone into the pond as follows: Situation 1a: the repeater is silent, no one is around...
Note a couple of things about the plot above: The "passive" opening gambit. The pauses. The retreat. Situation 1b: the repeater is silent, someone is around...
Note a couple of things about the above: it's strictly back and forth. DO NOT DROP THE REPEATER AND THEN START TO TRANSMIT AGAIN. Once you let go, no matter what you thought of next, do not TX again out of turn. At this point, the other guy has the baton. He may, if he realizes you had more to say, give control of the conversation right back to you. This is even more important when there are three or more in a round table on the repeater. Do not interject out of turn -- it is poor operating practice. We'll get to emergencies in a moment. Situation 2a: the repeater is silent, someone is around, and someone joins briefly...
Situation 2b: the repeater is silent, someone is around, and two people briefly meet up then move on...
There are a couple of important concepts illustrated above. First, the moment you let go of the PTT, the other guy you are speaking with has the ball. When the new arrival interjects his call prior to the beep terminating your transmission, it is NOT your responsibility to deal with him. It is the other guy you were speaking with. Likewise, as soon as the new arrival is finished, he gives it back to the other guy. In other words, the arriving guy slipped into the space between you and the other guy. When the arriving folks finish, the other guy has the baton and will deal with it however he wants. He may even turn it right back over to you with "hey keith, what was it we were talking about?" You can help the flow of any repeater QSO by finishing with "back to you, Ed" or similar. This is usually not necessary to keep two people in sync, but with three or more in a roundtable it's very useful (expected, really) to know who is before you and who is after you. The other little tidbit is that the arriving guy interjects his call prior to the courtesy beep. This is why you must ALWAYS wait for the beep prior to transmitting during the course of a normal conversation. Finally, there is an immense significance to the word "break" to amateurs. Do not use this word at any time on any repeater unless you are 100% sure you want everyone's immediate and complete attention -- this word signifies an emergency condition and you should never use it (or derivatives like "breaker") unless it's a bona-fide emergency. The important thing to remember is that it's like tennis. You do not get two swats at the ball. This keeps order in the game. I have a few tips for you. (1) Solicit feedback on your audio. this will help you learn how to speak into your radio. And (2) always wait for the repeater beep; this allows other stations the opportunity to get their call in as I showed above. Finally, (3), after you key the mike on your radio, allow a small amount of time before speaking -- a half a breath or so. There are a variety of relays, decoders, and so on that are actuated when the repeater goes from RX to TX. If you start speaking right away you may lose the first syllable. Good luck with your first QSO. It will go fine and you'll meet some nice folks. |
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Posted: 8/10/2007 9:03:35 PM EDT
[Last Edit: ar-jedi]
[#7]
using a repeater, part II There are two "goals" of repeater operation: (1) avoid doubling, and (2) avoid dead air. Doubling occurs when two folks transmit at the same time. The output of the repeater will be garbled, or one guy will overpower the other but when he drops the repeater you'll immediately hear that there was another guy talking. Dead air occurs when it is not clear who actually has the baton. Like in the Olympics, often this is a result of a poor handoff. For example, "I don't know who gets it next, but i'm done talking..." is an example of a poor handoff in a roundtable. Learn the NAME or CALLSIGN of the guy downstream of you. This is the most critical piece of info. You'll instantly recognize your call or name when someone is about to hand you the baton; if you do likewise, there will be no problem for the guy downstream from you. You'll note that dead air often leads to doubling, and doubling often leads to dead air. Both of these issues usually happen during busy sessions or when one guy loses track of who is the next in the roundtable. This happens most often with mobile operators, since it's (a) difficult to write things down while driving, and (b) your attention is where it should be, namely concentrating on properly driving and navigating a 4000 LB moving object. For this reason, I suggest that when learning the ropes you use a small notepad to write down callsigns and names on the repeater you are working. scribe the names and then you can draw arrows to show who is next etc. This will help you immensely at the beginning -- it's hard enough to figure out how things should be working when you are also trying to keep track of callsigns/names in your head. So write the latter down. Down the road, with practice, you will automatically keep track of the next guy in the list, and when he leaves the roundtable you can update the pointer in your head to the "next next" guy on the list. As a last resort: if you don't know or forgot who is next, give it to SOMEONE -- ANYONE in particular -- by using their name and/or callsign. It's far better to have a temporary "out of roundtable order" situation (which will quickly be rectified) versus having dead air and the inevitable doubling which will occur next. Some other thoughts... Commuting times are simultaneously the best time to make 2M repeater contacts but also could be the hardest if the repeater gets busy. Weekends are easier for beginners, as folks aren't so rushed and the roundtable won't be so dynamic with lots of folks coming and going as they start out for work or arrive at work. You will notice that on a given repeater there are different types of people with different types of personalities -- just like in actual life, say at where you work. You will observe that some folks are more than willing to help out beginners, some are always in a rush to get somewhere, some are retired and want to talk endlessly about their gall bladder surgery, some are tech heads and want to discuss electromagnetic theory, and others are there to chit-chat about Bush or the Sopranos because the repeater is in essence an extension of the water cooler at work. Different repeaters will have different "feels" due to the people who frequent them, again this is no different than your local bars. If you find a repeater crowd that fits with you, great. If not, spin the dial and try another. Or simply try another timeslot -- maybe the commuter crowd is not your clique. One last thing. Repeaters are run by repeater clubs. The club members, and other organizations, will likely have scheduled activities on the repeater. These are called "nets". For example, there may be an every other week "member net" on Tuesday at 8pm, wherein all the members get together to discuss repeater issues, improvements, or whatever. A second example is an emergency communications net -- you may hear the acronyms ARES or RACES during such nets. If you tune into the repeater during a net, of any type, you are not to transmit without understanding first what the net is about, and whether it is a "public" net. If it is not, it is time to shut up and listen only. Otherwise, you are simply interfering in an organized proceeding -- which is sort of like driving onto the oval during a NASCAR race and asking "what's going on guys?". When the net is done, the control operator (for example, a repeater club member acting in that capacity) will announce that the net is over, and that "the repeater is now returned for general use". At that point you are free to use the repeater once again. This just reinforces the amateur radio concept that you always listen first. |
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Posted: 8/10/2007 9:05:33 PM EDT
[Last Edit: ar-jedi]
[#8]
PL/CTCSS, aka tone squelch In normal FM ham radio communications, such as with a typical 2M radio, the speaker only emits the received signal when the received signal strength exceeds the squelch setting. In other words, you hear nothing until and unless there is someone talking on the frequency and their signal is strong enough to overcome the squelch threshold. You can of course increase the squelch setting to prevent weak, far away signals from being heard. However this approach may cause you to miss communications when your buddy is inside a building or behind a hill, making his signal weak. Similarly, increasing the squelch level on a repeater causes more problems than it solves -- the biggest problem being that weak signals from portable HT's are now unable to bring up the repeater. This completely defeats the intent of a repeater in the first place -- that is, giving low power stations good communications coverage. As you can see, using the squelch setting alone to discriminate stations doesn't work for repeaters. If the squelch is set too low, distant stations will bring up the repeater, even though they have no hope of being intelligible over the noise floor. Even intermod from other nearby transmitters would bring up the repeater. If the squelch is set too high, well we have just excluded folks with HT's from the repeater user base unless they are quite close to the repeater. Suppose, instead of just using the squelch level, we also employed some other (additional) way to discriminate legitimate signals worthy of repeating versus those signals which should not be repeated. If valid users could send a signal to the repeater that indicates they REALLY want to be repeated, it would be most helpful and completely end the "where to set the squelch" guessing game by the repeater operator. In the early 1980's Motorola brought out this feature for commerical/public service radio users and misnamed it "PL" for "Private Line". (note: there is nothing "private" about it in terms of encryption or even obfuscation). Commercial/public service radio users with repeaters face the same problems that amateur repeaters face, as described above. So Motorola designed a system whereby the remote radios would transmit a very low frequency (subaudible) tone along with the voice audio when the mic was keyed. The repeater says to itself "ok, i'm receiving a valid signal that clears the squelch setting -- check; AND that signal includes the PL tone that i'm looking for -- check. So, I'll repeat this signal." As you can see, there is now a two part check at the repeater: (1) signal strength and (2) correct PL tone. This eliminates a lot of "falsing" at the repeater -- weak transmissions and/or intermod no longer erroneously bring up the repeater. Hence, don't think of PL as some sort of barrier to using a repeater. PL is employed to make the repeater MORE useful, MORE available, and MORE enjoyable. In addition, with PL in place the squelch can be set lower and this will increase the repeater's coverage area. Some repeaters, by the way, employ "dual mode squelch": if the received signal is strong enough, no PL is needed to bring up the repeater. However, weaker signals require an accompanying PL tone. This is sort of a "best of both worlds" approach but really only works when there are no nearby strong intermod sources. Later on in recent history, the trademarked Motorola term "PL" was given a more representative, accurate acronym: CTCSS. Continuous Tone Coded Squelch System. Continuous / because the tone is present whenever you are transmitting. Tone Coded / describes that a tone is sent with the voice Squelch System / which is exactly what it does (versus that "private line" nonsense) --- DCS (digitally coded squelch) is a newer selective squelch system which sends low speed digital data along with the audio. repeaters can use theis data to enable the output transmitter, just like PL does. DCS is rarely used in the amateur community at this point in time, for a lot of reasons. The biggest is that only recently have ham HT's and repeaters become available with DCS features. If you set up a repeater with DCS access, you will end up with a only a very small group of users who have the latest (~2005 on) radios. --- The real value of digital selective squelch systems is in modern commercial/public service trunking systems, where additional digital codes either at the beginning of the transmission or on a separate control frequency are used to arbitrate and select talk groups. This allows maximal frequency reuse in busy radio environments (like NYC), and rapid centralized assignment/re-assignment of talk groups (like connecting a subset of NYPD radios to a subset of FDNY radios during a rescue operation). --- Hope all that helps explain the technical rationale for selective squelch systems. ---
Almost all modern VHF/UHF HT's and mobile rigs will scan for and then display the received PL. On my Icom V8000 mobile for example, you hold down the TONE button for 1 second and it begins stepping through the PL tones (about 5 per second). When it finds the correct one it stops there and displays it. Similarly my Yaesu VX6R will auto-determine both PL and DCS (although DCS is rarely used on amateur repeaters). If you are considering a certain model radio, go to the manufacturer's website and download the PDF manual. There you will learn whether the feature is available and how to make use of it.
Some repeaters do strip the PL, but most do not. Hence, on the output of the repeater you should in most cases be able to detect the PL. If not, you have to listen on the input (typ +/- 600KHz on 2M, +/- 5MHz on 70cm)
Understood. The PL search feature is very handy when traveling as you may not be able to read a repeater book (ARRL or Artsci) while you are driving. I don't think ANY amateur radio operator/club is going to get wound up to any degree if you respectfully use their repeater. On occasion you may inadvertently intersect with some repeater activity (say a RACES drill, or an about-to-happen repeater club check-in) but that's the case on ANY repeater. You'll be politely asked to simply listen or QSY to another repeater. |
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Posted: 8/10/2007 9:09:34 PM EDT
[Last Edit: ar-jedi]
[#9]
ham radios vs CB radios vs FRS/GMRS/MURS radios: why don't they interoperate with one another?
(1) CB and FRS/GMRS are two total separate things. CB operates at around 27MHz and uses AM modulation. FRS/GMRS operates at around 460MHz and uses FM modulation. there is no way to communicate with CB radio at one end and a FRS/GMRS radio at the other end. note: you may have been led astray by none other than the FCC... on their web pages, they refer to all unlicensed "civilian" radio allocations as "Citizen's Bands". but the old school CB units we all know and love from Smokey and the Bandit DO NOT interoperate with the new FRS/GMRS radios.
(2) no ham radio (aka amateur radio) transmits on CB frequencies. for that matter, there is no such thing as a multi-mode ham radio in that it transmits on ham AND another band (marine, CB, GMRS/FRS, etc). ham radios transmit on ham frequencies, period. so the answer to your question is "no" -- a V8000, FT8800, IC208H, etc can not communicate with a CB radio. besides the fact that CB is AM at around 27MHz, and a 2M radio is FM at around 146MHz, it is not lawful to use an amateur radio on CB frequencies. in summary, you'll need both types of rigs. if this poses a mounting problem, look into the 2M and 70cm radios that have remoted faceplates. the main unit can be mounted under the seat (etc), and only a very thin faceplate is mounted on the dash or other area. the very first post in this thread contains a link to pictures of installed radios, and many of those pictures show both a ham radio and a CB radio.
no. see above. that covers the non-ability of using a common VHF/UHF mobile (or HT) ham radio on frequencies assigned to CB's. now then, most HF-capable amateur radios can receive AM in the CB band, so you can listen to CB. but no HF-capable amateur radio transmits on CB band. in summary: ham (amateur) radios are SINGLE PURPOSE: they transmit on ham bands only. while many ham (amateur) radios have wide band receive (and scanning features) so you can listen to all kinds of things like NOAA weather (~162MHz FM), police/fire/EMS (~150MHz/450MHz FM), aircraft (~120MHz AM), and so on, these radios do not transmit outside of the amateur bands. --- ham radios generally fall into two categories, HF and VHF/UHF -- although, within the last few years several ham radios that TX in all ham bands HF to UHF (and all modes) in one unit have become available. (modes = AM, FM, SSB, CW). the typical 2M-only VHF mobile ham radio will TX 144-148MHz FM, but RX from 137-168MHZ -- which covers all of the NOAA weather and public safety "high band". some 2M mobiles also RX "air-band" around 120MHz, in AM mode. the typicial 2M/70cm VHF/UHF "dual band" mobile ham radio will TX 144-148MHz and 420-450MHz, and RX 137-168MHZ and at least 400-470MHz. public safety agencies not on the 150MHz band and not yet converted to 800/900MHz digital trunked systems can be found in the 450-470MHz range. some 2M/70cm mobiles RX "air-band" around 120MHz, in AM mode, and also RX "mil-air" around 300MHz in AM mode. the typical desktop HF ham radio will RX *at least* from 1.8MHz to 54Mhz continuous, again across all modes. This covers the 160M to 6M ham bands, and shortwave radio stations, and a million other things. as for TX, there are defined areas within 1.8-54MHz where the transmitter output will be enabled. operation outside those areas is unlawful. as you can see, it is possible with a HF ham radio to RX CB frequencies (~27MHz AM) -- but TX is inhibited. |
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Posted: 8/10/2007 9:13:32 PM EDT
[Last Edit: ar-jedi]
[#10]
buying a radio (VHF/UHF-centric)
as noted above, ham radios come in basically two flavors: HF and VHF/UHF. for mobile applications, you want a VHF/UHF type. this will give you point to point communications with another ham at a range of about 20 miles, depending on terrain. using a repeater, that range can be extended up to 50 or more miles.
with the same external antenna, a proper mobile radio will provide a better solution than using an HT (handy-talkie). the HT will have at max about 6W output, in contrast the mobile will have 8-12 times that (50 to 75W). moreover, the antenna connector on a modern HT is somewhat fragile, and will not appreciate constant connection and disconnection. to continue, a mobile radio is much more tolerant, thermally, of long transmissions versus an HT. at 6W output, an HT is going to get hot, there is no way around that. finally, the larger speaker on the mobile will make it easier to hear incoming transmissions in the noisy cab of your truck. for these reasons, and several others, i recommend that your first radio be a true mobile rig, and not an HT. that said, good 2M HT's are quite inexpensive; you can pick up a Yaesu VX170 for about $130. so getting a mobile and then getting an HT a bit down the road is the usual approach. btw, i speak from some experience here. i initially used an HT for a mobile. over the course of a year (~1991) i wore the nubs off of the BNC connector. i replaced it. i didn't learn from this. somewhat later, the internal wire connecting the BNC to the RF power amplifier broke. disassembly time again. summary: get a mobile for your truck. the reliability and the audio output level will make it much more enjoyable.
basic "starter" systems... (a) 2M (VHF) only: Radio: Icom V8000 Antenna: Comet SBB5-NMO (NMO mount). Mount and coax: NMO type, attachment dependent on installation (trunk lip, gutter, through-hole, magnet, etc) (b) 2M/70cm (VHF/UHF aka "dual band"): Radio: Yaesu FT7800 (or FT8800 if you can spring for another $100) Antenna: Comet SBB5-NMO (NMO mount). Mount and coax: NMO type, attachment dependent on installation (trunk lip, gutter, through-hole, magnet, etc) with both (a) and (b) above, if your local PD/EMS is operating in the 150MHz range, you'll be able to tune into them. you'll be able to RX NOAA weather on 162MHz as well. setup (b) will allow you to listen into your local PD/EMS if they are in the 450MHz band. neither (a) or (b) will help if your local PD/EMS is in the 800/900MHz band or if they are using a digital trunked system. note that i selected the same antenna for both applications above. the cost differential between a 2M and a 2M/70cm (dual band) antenna is minimal. so, by buying a dual band antenna right away you will avoid having to get a new antenna if you decide to change out your mobile or you get a dual band HT that you want to use in the truck. ---
no. in fact, that rubber duck gives the worst performance across the bands. a longer antenna will give better wideband receive than the stock antenna. don't get hung up on this -- to reiterate what i wrote above, ANY modern VHF/UHF amateur radio has sufficient out of band sensitivity that the choice of antenna is somewhat irrelevant. this in fact can be a problem in urban areas when using HT's in a car with a external high gain antenna (e.g. a 5/8 lambda whip). the high sensitivity of the HT, combined with the high gain of the antenna, make for a nice recipe for intermod from nearby high power transmitters (pagers, taxis, commercial radios, etc). intermod, for those just starting out in amateur radio, is interference on your radio from sources other than those on the frequency you are tuned to. even though the transmitter may be on a wholly different frequency, the strong nearby signals overload the front end of the receiver, which unsquelches the audio -- and you hear a distorted, unintelligible sound from the speaker. in commerical radios, resistance to intermod is greatly improved by the use of narrowband RF filters as part of the front end. this prevents unwanted out-of-band frequencies from reaching the discriminator circuit. commerical radios sit on one unchanging frequency though, so the rejection filter(s) can be quite narrow. why can't these types of filters be employed on amateur HT's? because we want super wide-band RX, that's why. you can't have your cake and eat it too here. either you have narrow front end filters and very little tuning range, OR you have wide/no front end filters and a very large tuning range. in the latter case some unwanted signals are going to slip in. in an amateur HT, the combination of no/wide front end filters and very high sensitivity make for an intermod-prone solution when used with an antenna other than the stock duck antenna (aka 50ohm rubber resistor). this is generally not a problem out in the fields of kansas but in urban areas you may find that you are much better served with a proper 2m-only mobile rig. ---
FOR YOU: get the VX6R, great 2m/1.25/70cm radio with wideband AM/FM receive. get a short, very flexible duck antenna so you can put the radio in your vest without putting undue stress on the SMA connector. get an SMA->BNC adapter, and a short piece of RG58 coax with a male BNC on one end and an PL259 on the other end -- all this so you have some external antenna flexibility, for example connecting your HT to a mag-mount 5/8 lambda car antenna in a pinch. get the external power cable (E-DC-6) and add on a pair of alligator clips with an inline 1N4001 diode for reverse polarity protection. FOR YOUR CHARGES: get qty 2 of yaesu VX170 2M radios. get qty 2 of the 4 x AA battery packs (FBA-25A) for SHTF use. i can't think of a better, more reliable, simple-to-operate HT than the VX170. it's a great value for the (current) price. get another one or two E-DC-6 power cables and attach a cigarette lighter adapter plug. even if a car battery it too weak to start a car it will run a VX170 for 10 days. --- i'd like to make one final comment here: a technician class amateur radio license is required to transmit using any of the radios above. licensing exists for a reason: to make the hobby enjoyable for everyone by getting folks educated about the art of amateur radio communications. the technician class test is very straightforward, and can be studied for in a few nights. you will be in and out of the exam session in 20 minutes flat. there is simply no excuse for not getting a license before transmitting. |
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Posted: 8/10/2007 9:19:32 PM EDT
[Last Edit: ar-jedi]
[#11]
how to find your local repeaters
paper version --> www.artscipub.com/mapbook/ online version --> www.artscipub.com/repeaters/  don't ignore eventually getting the paper version; when you are traveling, it is very handy to have a repeater book in your glove box/map pocket. there is also a palm-sized repeater guide published by the ARRL; click the following link: www.arrl.org/catalog/?item=9906  note that getting a repeater book is *not* a yearly expense. from my experience (ham licensed since 1991), a repeater directory is good for about 5 years. this is because there is very little "turnover" in ham repeaters, so it's not like the data is changing all of the time. in fact, if you can pick up an older 2005 or 2006 edition book for a buck or two at a used book bookstore, grab it. i'd say that 99% of the repeater information inside will still be useful for the next couple of years. the data in the repeater books/websites will be as such:
this means that the repeater is located in Middletown, NJ, with the repeater output on 145.485MHz, with a (-) (=minus) offset. the usual offset for the 2M band is 600KHz, or 0.600MHz. so, 145.485-0.600=144.885MHz. this is thus the input frequency -- but note that in some repeater books (like the ARRL's), due to space reasons they show the offset direction but don't show the actual input frequency. others do, like the example above that i pulled off of the artsci web page. aside: with most modern rigs, the radio is preprogrammed with a 0.600MHz offset, and the offset direction is calculated automatically from the tuned frequency. one radio manufacturer calls this "ARS", for "automatic repeater shift". the radio "knows" which way the offset direction is because of the standardized 2M bandplan. that is, repeaters between M and N MHz offset UP, and repeaters between X and Y MHz offset DOWN. i don't remember offhand the exact frequencies for the repeater allocations in the 2M bandplan but you get the point. the next number over in the example listing above, 151.4, is the PL/CTCSS tone frequency (in Hz). without setting up your radio to emit this PL tone while you are transmitting, the repeater will not activate. with most modern radios you first must set the PL tone frequency, and then enable transmission of it. both steps are required. finally, the last item in the repeater listing is the FCC callsign of the repeater trustee or repeater group, in this case N2DR. --- also see www.usrepeaters.com/ |
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Posted: 8/10/2007 9:24:13 PM EDT
[Last Edit: ar-jedi]
[#12]
mobile antennas and mobile mounts
+1 million. the NMO mount antenna will not become a hazardous flying object if/when you get into an accident like a mag mount will. the NMO mount antenna will not damage your car finish like the dirt trapped under a mag mount will. the NMO mount antenna will not fly off when you hit a frost heave on the highway at 80 MPH like a mag mount will -- leaving scars where it bounced along the side panel of your car while you slowed down. the NMO mount antenna will be imtimately grounded to the chassis of the car, and will exhibit better performance (=range and noise immunity) than the capacitively-coupled mag mount. summary: there is a reason that law enforcement, government, commercial, industrial utility, and other applications rely on the NMO mount --> it works. losdos.dyndns.org:8080/public/ham/tacoma-icom-v8000/DSCN1588_sm.jpg losdos.dyndns.org:8080/public/ham/tacoma-icom-v8000/DSCN1585_sm.jpg losdos.dyndns.org:8080/public/ham/tacoma-icom-v8000/DSCN1581_sm.jpg
for those unfamiliar with this type of mount, see the pics of my 2m/70cm truck antenna intsallation, near the top of page 11 in this thread... ar15.com/forums/topic.html?b=1&f=123&t=486162&page=11
the 3/8" hole version (developed by Antenna Specialists) is fairly new (a few years) and of course needs a smaller hole than the original Motorola-designed 3/4" version. above the sheet metal they are exactly the same, that is they both accept all NMO mount antennas. the two sizes differ only in the mounting hole diameter. that said, i have heard from more than one person that the 3/8" version, because of the ferrule it uses, is less-than-watertight compared to the normal 3/4" version. moreover, evidently on some models the coax exits straight down with the 3/8" version, compared to the right angle of the 3/4" design. hence, the 3/4" version needs less underside clearance. so i side with the 3/4" version because it is tried and true; the mount in my pics above is a 3/4" type. it is a MAXRAD part number SMML195-NC, a commerical quality stainless steel 3/4" NMO mount w/ 17' of LMR195 low loss coax -- a very nice setup. see www.maxrad.com/cgi/images/products/pdf/StainlessSteelMSeries_p67.pdf or more generally www.maxrad.com/product_category_detail.cgi?id_num=28&styleid=8 MAXRAD mounts are available from Hutton Communications Harrisburg PA Office 800-759-3031 https://www.huttononline.com/HuttonOnline/mobile.aspx?cat=10 (aside: why did i go stainless vs brass? i live 100yds from the atlantic ocean -- crap corrodes around here like you would not believe. the PN above is the exact type that the radio guys who outfit our local police and county sherrif's cars use.)
the connector on the back of a 2M rig is called by several names, including "UHF connector", "SO239", and "PL259". the first two are "more correct", with SO239 being exact. SO239 describes the female end (on the radio) and PL259 describes the male end (on the coax). this, btw, is the same two connectors that CB radios use. note that the SO239/PL259 pair is NOT weatherproof so it should never be used for outside applications. moreover, it is not a great connector for frequencies above 150MHz; even for 70cm use (440MHz) it is a compromise. there is a reason that BNC and N connectors exist: they are markedly better RF-wise and they are weatherproof in contrast to the inexpensive SO239/PL259 pairing.
MAXRAD is commerical quality but most NMO mounts i've seen are pretty decent.
also see models from Diamond and Comet. note that the NMO mount part number i referenced above does not include a connector at the radio end of the coax. so you need to procure and solder a PL259 onto the coax after you are finished reeving the coax cable over the hills and through the valleys from the roof down to wherever you mount the radio. get an AMP brand or Amphenol brand PL259, and not some junk from radio shack (which are plated crap connectors). wherever you get a quality mount from will be able to supply you with a quality PL259. make sure to get the solder-on type, and not the crimp-on type. the crimp-on type requires specialized (expensive) tools to attach to the coax. one more thing: you install an NMO though a hole in the sheetmetal of your vehicle. i know this sounds scary. will it leak? the answer is no -- millions of taxis, police vehicles, gov't vehicles, and so on use the NMO mount without problem. it is the best mount avaliable from a weather, RF, and reliability perspective.. the best ways to make the mounting hole are (1) use a 3/4" dia chassis punch, or (2) use a step drill made for specifically this purpose. the former is available wherever Greenlee punches are sold, and the latter can be hard to come by but consult with Google. i use a chassis punch. |
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Posted: 8/10/2007 9:31:32 PM EDT
[Last Edit: ar-jedi]
[#13]
suggestions on radios and accessories
i assume you are talking about getting a VHF/UHF radio first... IMHO:
as for a base. there are two ways to go here, and they are as follows: get a mobile (aka compact) rig and an external power supply, OR get a proper base station radio. now then, in light of recent regulatory developments, i'd suggest that you start saving your pennies and pick from one of the following radios which will give you VHF/UHF and HF capabilities:
if you go with separate VHF/UHF and HF rigs, i would not hesitate to recommend the Icom IC718 -- it really is the HF amateur radio bargain of the century. www.eham.net/reviews/detail/947 all of the above assumes you want to go with a new rig. if you want or can only afford a used rig, scan the reviews at Eham for high ratings and then watch the Eham and QRZ.com classifieds. or, if you come across a good rig (like a IC735 or TS50) at an estate sale, snap it up.
-- get a battery pack that accepts AA's. then get a 6 pack or two of Lithium AA's (very long shelf life). -- construct/buy a roll-up J-pole antenna made from $0.89 worth of TV twin lead. will extend your range 10-fold. -- buy a suitable power cable to connect the external power in jack to a cigarette lighter, so you can always power/recharge the HT in the car. -- construct/buy/McGuyver a soft case so when you drop it (inevitable, btw) it doesn't break your heart. -- get a 4AH, 6AH, or 12AH gel-cell/AGM battery and a suitable power cable so you can use your HT for a couple of days while without commerical AC power. -- scroll back a few pages in this thread to where i posted a list of recent ham radio-related links, and find the one that has SF'er Rjsteed's setup in it. this will give you lots of ideas on how to make a convenient, pack-portable setup for on-the-go comms. -- look up the origin of the ham radio signoff "73" and report back to us. ---
ok, you are on the right track with both of the links you picked out...
the design above is a center-fed vertical dipole. one advantage is simplicity of construction; however there are several practical disadvantages; namely that the feedpoint is halfway up the antenna, and that the feedline must "exit" the antenna proper at a 90degree angle for some distance (at least 1 meter would be a good idea). the combination of these two issues make for a more cumbersome hanging arrangement in a field expedient design. the result of the feedline hanging down too close to the lower element of the antenna will be poor field uniformity. moreover, by driving a balanced antenna (dipole) with an unbalanced source (HT) and transmission line (coax), you are all but guaranteed to have feedline current on the shield. this will make the antenna even less uniform from a gain perspective -- you may find a big lobe in one direction and poor performance in another. that said, the dipole is of course a proven design and if you can solve the "how to hang it" issues it will work well.
the design linked above is a 1/2 wave J-pole. the Jpole is a method of end-feeding a half wave radiator. properly constructed, performance will be on par with the dipole, and the easier "hanging" of the Jpole make it more useful as a field-expedient antenna. you are right about the 37.25" piece -- it is just along for the ride. the real work is done by the radiating element (54") and the matching section (15.25"). while the thought of driving a dead short such as is found at the bottom of the Jpole may scare you at first, in RF-land things work a little different. IMHO, for SHTF applications, the Jpole is the antenna of choice due to low cost, ease of construction, ease of hanging, and good overall performance. ---- in both of the cases above, the coax type should be RG58 (50ohm characteristic impedance) and you will terminate the coax with a BNC connector. the SMA is not suited for RG58 coax, so the best way to get to attach the coax to the HT is to use a BNC<-> SMA adapter. these are very commonly available at ham places for a couple of bucks. see "#0531 -- SMA M-BNC F -- SMA male to BNC female adapter" here: www.universal-radio.com/CATALOG/parts/smadapt.html ETA: you can also get a short patch cable, such as the HB05 as is shown here: www.universal-radio.com/CATALOG/hamantht/4454.html  note that using this type of adapter cable will impose less stress on your HT's SMA connector than using a BNC<->SMA adapter. this is because the coax shown above is more flexible than the typical RG58. ----
if you have the coin, you can get an Icom 706 MkIIG. one of the best radios ever. decent receiver, 100W out on HF, 50W on VHF, and 20W on UHF, all in a very small form factor. it is a tad thirsty on RX (~1.5A) so keep that in mind when operating from batteries. www.icomamerica.com/products/amateur/706mkIIg/ www.icomamerica.com/products/amateur/706mkIIg/specs.asp www.eham.net/reviews/detail/63
icom 706 MkIIG. then sneak a $140 2M mobile into the truck a few months later.  www.gigaparts.com/store.php?action=profile&flash=1&sku=zic-706mkiig |
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Posted: 8/10/2007 9:37:22 PM EDT
[Last Edit: ar-jedi]
[#14]
lightning protection / station grounding
great radio, a great start for you.
perfect, excellent, outstanding in fact.
yes. the right way to do is this is to make a bulkhead entrance panel. for example, get a small sheet of 1/8" aluminum and drill a hole to accept a UHF bulkhead connector (female to female). mount this as part of the exterior wall on your basement. the coax from the antenna screws onto the outside, the coax from the radio screws onto the inside. the aluminum panel should be grounded by using a hefty piece of #6 AWG wire running to one or more copper grounding rods driven into the earth. a lightning protector (Polyphaser brand is OK, but I.C.E. (*) is the best) should be installed on the outer side of the bulkhead, and the ground tied to the aluminum panel. (*) see also www.iceradioproducts.com/impulse1.html#1 and especially www.iceradioproducts.com/thorshammer.htm#top%20of%20page  also check out www.dxengineering.com/Products.asp?ID=212&SecID=112&DeptID=19 and follow the link to "Lightning Protection Tech Articles" within.
you need good coax, nothing less than RG8, perhaps 9913F7 or LMR400. don't skimp, every dB lost on the way down to your radio means fewer stations that you will be able to hear.
yes, that's what is common on HF and VHF gear.
perfect. see lightning protection strategy outlined above and read the following: www.iceradioproducts.com/30.htm www.iceradioproducts.com/31.html www.iceradioproducts.com/31a.htm <------ !!!!
i would not interconnect your antenna system with the house grounding system. i say this for two reasons... one, your antenna system is an attractive lightning target (even a nearby strike is going to couple thousands of volts into the antenna). this is not voltage/current you want in the house, on the house ground system. you want to keep this out of the house when possible, in order to prevent any collateral damage. two, you may have an ineffective or otherwise compromised house grounding system, and it may not provide an adequate path for the high currents induced by a direct or nearby lightning strike. for the reasons above, i suggest that you keep your house and antenna grounds completely separate. this means that the metallic tower should be grounded, and then the antenna downlead(s) should be grounded/protected using the bulkhead panel method i outlined above. regarding the grounding rods, more is better than deeper. two or three 6' long rods, driven in approximately 6' apart and interconnected with heavy guage wire, make for an optimum ground. keep in mind that the above methods, while not guaranteeing 100% that you will never have lightning damage, is far greater protection than most folks employ. in areas such as Florida (the lightning capital of the US), i would say that the above approach is mandatory.
the SMPS will not have any problem cleaning up the power. ar-jedi ETA ps: you may want to browse through the following: www.eham.net/forums/StationBuilding --- members.cox.net/pc-usa/station/ground0.htm www.comm-omni.com/polyprod2.htm --- Get grounded: protecting electrical devices from lightning transients (Part 1 of 2) www.planetanalog.com/article/printableArticle.jhtml?articleID=201807127 Get grounded: protecting electrical devices from lightning transients (Part 2 of 2) www.planetanalog.com/article/printableArticle.jhtml?articleID=201807830 |
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Posted: 8/10/2007 9:43:14 PM EDT
[Last Edit: ar-jedi]
[#15]
more info on mobile antennas 1) I have about settled on the Icom V8000 2M mobile. Since I want a "pro" installation and I don't know any hams yet IRL, should I have it installed? I know where I want it installed. You think a stereo shop could do the physical install or should I seek out a 'radio shop'?
the V8000 is an excellent radio –– i have two. the front facing speaker is great, and the unit is very tough. mounting and powering the radio is not at all complicated –– you can do it yourself in a few hours. if you want to get "pro" help, i would look for a place that installs two way radios. look in the yellow pages for a "Motorola" or "Vertex" installation shop. they will have the necessary know-how and tools to not only put the radio where you want it but also route your antenna coax. 2) What are a few 2M antennae which are generally considered solid? you need two pieces: the mount and the antenna. the mount comes with coax attached (usually about 15-17 feet). the choice of the mount is dependent on two things: the surface type you are mounting to, and the connector which will interface with the antenna proper. for the first part, antenna mounts are offered in gutter rail mount, trunk lip mount, through-hole mount, mirror arm mount, and others. you just need to decide where you are going to mount the antenna and pick a mount type. you will note that trunk lip mounts have a short piece of very thin diameter flexible coax which allows the coax to pass through the seal without causing a leak or causing damage to the coax itself. good mounts come from Diamond, Comet, Larsen, and Maxrad. for the antenna connector, there are really three choices: NMO, UHF, and N. let's start at the end, the N connector. the N has unparalleled frequency capability and is completely weathertight, and therefore is only the choice for 900 and 1.2Ghz mobile operation. however, you will generally not want to use an N for 2M/70cm work as the number of 2M/70cm antennas with N connectors is limited. the UHF connector is the tried-and-true PL259/SO239 combo. it sucks at almost everything: it is neither constant impedance nor is it very good at 440MHz/70cm nor is it designed to be weathertight. antenna manufacturers have done their best but it does have its limitations. there are many many 2M/70cm antennas with the UHF connector. which brings us to the NMO. this Motorola-designed connector was built from the ground up for mobile applications. it is weathertight, has excellent frequency span, and there are a bajillion commercial/industrial/public safety users out in the Real World using it every day. this is the very same connector you see at the base of the antenna(s) on any police, EMS, or firefighting vehicle. the NMO is the connector type you should use. now then, once you have decided on a mount and connector type, you can pick an antenna. it obviously must have the mating connector on the bottom. the height is the primary influence on performance, though there is one other important factor which i'll discuss in a moment. however, taller antennas drag on garage doors, attract more attention, and put more stress on the mount. so it is a tradeoff. nevertheless, i would not choose a 2M/70cm antenna of less than ~19 inches. there are too many limitations below that length and moreover you don't really want to shove 75W into an antenna that small. reputable antenna vendors include Diamond, Comet, and Larsen. 3) I plan on mounting the antenna on the back of my Jeep very near the spare tire. Can I take any special precautions not to let it touch the tire, or should I reconsider the mounting location? i mentioned above one other factor... some antenna designs, such as the 1/4wave ground plane, rely on –– you guessed it –– an underlying ground plane for good performance. should the ground plane not exist (say on a fiberglass roof) or should the ground plane be asymmetric (for example, if you mount the antenna in one corner of the roof), the antenna will not operate to your expectations. you may have problems getting the SWR to sit down as well. keep this in mind as you pick an antenna type. it may not be easy for a beginner to determine what mobile antenna designs are "more compatible" with a given mounting location. in that case, post a pic of where you'd like to mount the antenna, and what height you are looking to use, and we can make some recommendations. |
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Posted: 8/10/2007 9:45:39 PM EDT
[Last Edit: ar-jedi]
[#16]
Building your own repeater
it's not simple. there is no way to build a modest size radio that does "same band repeat". it certainly can not be done in an HT or mobile radio. the problem is that the TX output saturates the RX input, causing desense. the net result is that your "pseudo-repeater" is nearly completely deaf and for the most part is listening to itself. in a "real" 2M repeater, there are cavity duplexers which provide DEEP notch filtering on the input to the RX, with the notch centered directly on the TX frequency just 600KHz away. the absolute best way to get the depth of the notch you need is via a mechanical cavity filter, and not some collection of discrete components. typically, you will need between 60 and 100dB of TX to RX isolation in order to have an effective repeater. note that you can sometimes "cheat" by using seperate TX and RX dipole antennas, and putting one about 20-40 feet directly above the other. this gives some isolation but does not completely solve the problem. so you are back to needing a cavity duplexer. in general, the selection, procurement, and tuning of the duplexer(s) are the most difficult parts of a repeater construction project. hence, the reason that your radio will never do same band repeat is because the cavity duplexers for 2M are roughly the size of large gas welding tanks. so you'll need: two radios, a repeater controller, an antenna, and most importantly, a duplexer. the duplexer is the key to the whole operation. the TX and RX frequencies for a 2M repeater are separated by a mere 600KHz. isolation between the two is critical, assuming you want to use one antenna. a proper duplexer is neither cheap (~$500 -> $2000) nor small (think medium size water heater).  link --> http://www.repeater-builder.com/rbtip/repeater101.html see www.repeater-builder.com/antenna/w6nbc-duplexer-index.html www.repeater-builder.com/rbtip/2mduplexer.html
ps two asides: 1) "cross band repeat" on HT's and mobile rigs works because the TX and RX frequencies are widely separated (by hundreds of MHz), and this in turn makes filtering the TX RF on the RX input much less critical. you'll also note that duplexers for the 440MHz/70cm band are easier to design and build, due to the fact that the offset in the 440/70cm band is 5MHz, in contrast to the narrow 600KHz split used on 146/2M. 2) nothing, besides the repeater band plans and de facto operating practices, prohibits you from having a larger than 600KHz split on the 2M band. for example, you could RX at 144.05 and TX at 147.95. that is an almost 4MHz oddball split. this would make design of the duplexer easier and potentially allow it to be constructed much smaller than the typical 2M 600KHz split setup. nevertheless we are still not talking about something that you can hang on your belt. see also these pics for examples of duplexers: obra.aginet.com/photos/duplexer7.jpg oh3tr.ele.tut.fi/~ftp/repeater/filter/2m/oh2raa_duplexer.jpg www.ipass.net/teara/packet/duplexer.jpg www.svol.net/~ke3jp/146445%20duplexer.JPG obra.aginet.com/photos/duplexer8.jpg www.w6bxn.org/_borders/repeat2.jpg |
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Posted: 8/10/2007 9:46:14 PM EDT
[Last Edit: ar-jedi]
[#17]
crossband repeat with a dual-band mobile radio what are some decent mobile radios which can be used as repeaters for my HT?
the Yaesu FT8800 comes immediately to mind. it has a good rep (check eham's reveiws) and moreover it is very straightforward to set up LEGALLY as a crossband repeater. some mobile rigs are tough to convince to do simplex crossband repeat, which is the correct, legal way to do it. the in-car mobile radio should ONLY crossband the 440MHz input from your HT onto the 2M input to the repeater. it is neither necessary nor strictly legal for the in-car mobile radio to crossband the 2M output from the repeater onto 440MHz towards your HT. the latter is superflous as your HT has more than enough sensitivity to hear the output of the repeater. this scheme meets the letter of the law in terms of ID'ing ALL of your station transmissions. the general method of full crossband repeat does not. any time the repeater output is active, your crossband mobile radio will be TX'ing on 440MHz. if you went to sleep, the mobile would continue to crossband and thus you are violating the ID-every-10min rule right off the bat. two other advantages of this simplex crossband repeat configuration are that the in-car radio will stay much cooler and vehicle battery consumption will be markedly reduced as well. n.b. to configure simplex crossband repeat on the FT8800, set the 440MHz side TX offset to an absurdly high value, such that the transmit frequency falls outside the 70cm band. when the 2M repeater is active, the FT8800 would normally be trying to crossband it onto 440MHz, but now the FT8800's display will show ERROR as it is refusing to TX outside the 70cm band. in this configuration there will be NO 440MHz emissions from the FT8800. when your HT is transmitting, the FT8800 will RX on 440MHz and crossband that to 2M, which will be set to the 2M repeater input frequency. your HT should be set for "split" or "crossband" operation. TX on 440MHz to the vehicle, and RX on 2M from the repeater. So I'm just bragging today. I'm pretty excited about my crossband repeater. Now that its set up, it will only take seconds to get the radios ready when I go hunting.
a few words of caution. (a) the way that you have it configured, if the club repeater is a busy one your truck radio and battery will both have very short lives. a typical mobile radio is not designed for high duty cycle (meaning lots of TX time) applications. it will get hot, very hot, fairly quickly with an active club repeater. and when set up for full duplex crossband, your radio will be be pulling 5, 8, 10, 15A or so (depending on your 70cm crossbanded power output) whenever the club repeater is active. in general, the club repeater output is going to be active more than you will be active with your HT, so the primary contributor to current draw and heat generation is crossbanding the club repeater output. (b) the setup you describe is, to the letter of the law, illegal. the issue is that transmissions from the crossband repeater are not guaranteed to be ID'd by the station operator every 10 minutes. while the club repeater is active, but you are not personally using the crossband repeater, there is no ID and this becomes the legality problem noted prior. if, for example, you left the crossband repeater active while you are hunting but decided to take a short nap or perhaps a swim, you have this exact situation. your mobile rig continues to crossband the club repeater but there is no ID on the output. both problems (a) and (b) above are easily avoided by configuring the mobile for "simplex crossband repeat" instead of full duplex crossband repeat. how does simplex repeat differ? in full duplex crossband repeat: from the club repeater:
the approach with simplex crossband repeat relies on the fact that your HT can very often hear the club repeater output just fine. hence it is NOT necessary for the mobile radio to crossband repeat the club repeater output. not doing so saves vehicle battery power and makes the entire setup completely legal since all transmissions from the vehicle are properly ID'd. in simplex crossband repeat: from the club repeater:
so what is different? for one, the HT is set up for "split" or crossband operation. the HT TX's on 70cm and RX's on 2M. most all dual band radios can do this –– for example it's simple to set up on a Yaesu VX6R. and second, the mobile radio is set up not to TX on the 70cm side with an active 2M input. this mode of operation is not straightforward to set up as it is not generally a feature documented in the instruction manual. nevertheless, most all dual band, crossband-capable radios can be set up this way using a small cheat. the popular FT8800 is such an example, on the case of this radio, set the 70cm side TX offset to a frequency outside the amateur band. then enable crossband repeat. when the club repeater is active (that is, the radio is RX'ing on 2M and attempting to TX on 70cm), the display will indicate "ERROR" as it will not TX outside the 70cm bandplan. however, the reverse direction (RX on 70cm, crossband onto 2M) will continue to work just fine. in this manner, the FT8800 can be set up for the desireable "simplex crossband repeat" mode. again: using this simplex crossband repeat concurrently saves you a ton of battery power AND prolongs the life of your mobile radio AND keeps you legal. ––- I really like the idea of being able to use a radio in my car or house to repeat for my handheld.
get an FT8800, keep the power down, and keep your conversation lengths to a minimum. no 2M/70cm mobile can be utilized as a true repeater –– it will simply get way too hot and you'll end up cooking the power amp. one trick that most folks employ on the FT8800 does two things: it helps you stay legal and it helps keep the heat to a minimum. it goes as follows... recall that with an HT you can generally hear the repeater, you just can't hit the repeater (too little power into a 50ohm rubber resistor antenna). so, you really only need the crossband repeat radio to repeat what you are TX'ing, not what the repeater is TX'ing. (some folks refer to this as simplex repeat). in other words, when you TX on 70cm, the crossband repeater RX's your signal and simultaneously TX's it on 2M. this is what gets you into the repeater. when the repeater TX's on 2M, the crossband repeater does nothing. you receive the 2M signal directly by using split operation on your HT (TX on 70cm, RX on 2M). by the way, this scheme improves the legality of the whole situation since the crossband repeater's 2M output is always ID'd by you. (in a normal crossband repeater setup, there is no way to "truly" ID the 70cm output per the 10minute FCC rule. if you turn off your HT but forget to turn off the crossband repeater, it will merrily contine repeating without any ID –– which should be your call). so how do we get the crossband repeater to do nothing when it receives a 2M signal (from the repeater), but crossband repeat when it receives a 70cm signal (from your HT)? on the FT8800, you can't directly do this. there is no "simplex repeat" mode to accomplish this. but, you can fool the radio another way... set the TX frequency on the 70cm side to a invalid frequency, outside the radio's TX range. say, 480.000 MHZ for example. now when the 2M input is active, the radio display will show "TX Error" as it is refusing to TX outside the amateur band. but when the 70cm input is active, the radio will happlily crossband repeat the signal. sneaky, but it works nice –– it's legal, and it saves on TX power dissipation since the crossband repeater is only making RF power for half the conversation. ––- Originally Posted By cliffy109:
I found a great link on cross band repeating. It describes both the simplex and regular cross-band. It also reminded me to set up tones to prevent accidental use of the truck radio. |
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Posted: 8/10/2007 9:48:08 PM EDT
[Last Edit: ar-jedi]
[#18]
notes on operating from batteries during SHTF i thought i'd post a few notes on power conservation and field-expedient power techniques for radio operations during SHTF... 1) PREP! if AC power fails, you'll have (a) what power is on hand (stored batteries, UPS's, and so forth) and (b) what power can be made (solar, genset, etc). line up your resources ahead of time so that you'll have primary and fallback sources during SHTF. also look at it from an immediate and long term perspective: "first i'll run from gel-cell, then i'll get the genset started to power the house heat, and i'll recharge the gel-cell while the genset is running." 2) to that end i suggest that every ham have at least one 12V 12AH battery on hand. these can be had for about $20 and vastly increases operating time compared to an HT's internal battery. and of course you can power a mobile at low power as well. (example) 3) buy or build any cables necessary to get power from a source into your HT, mobile, or base station. modern rigs have specialized power connectors so it's not alwasy easy to rig up a field expedient solution for the radio end -- especially on HT's. the power source end could be a pair of aligator clips, or an Anderson Powerpole, or a pair of 1/4" quick-connect (faston) tabs to mate with a gel-cell battery. don't forget to keep these cables where you can find them! 4) at the onset of a blackout, immediately disconnect the loads from your household UPS's (e.g. PC, plasma/LCD TV, etc) and then turn off the UPS via the front panel. you have no idea how long the blackout will last, and the batteries in the UPS store an appreciable amount of power. you may need that power in the next few days -- but you probably don't need to watch TV on your 50" LCD right now. the power stored in the UPS's gel-cell batteries can be used directly (by removing the batteries from the UPS) or indirectly (by plugging AC loads into the UPS's outlets). either way, a UPS makes a somewhat portable, quiet, but time-limited "generator". the trick is not to piss away those electrons during the early stages of the blackout. 5) there is a lot of power stored in random places your house -- which in turn can be used for comms. for example, make an adapter/converter to allow you to connect a battery from your cordless drill to your HT. modern cordless drill batteries are really stout and will give great perfromance. typical 7.2, 9.6, 12, and 14.4V drill batteries will power your HT or mobile radio directly. higher voltage batteries (e.g. 18V) will need a step down regulator. if you have a DC-powered backup pump for your sump, that may be another source. of course the lead acid/gel-cell batteries in your lawn tractor, motorcycle, and home alarm system can be used in a pinch. similarly, laptop computer batteries store an impressive amount of power, although the connector arrangements and voltage levels may make them difficiult to work from. but any/all of these could be utilized if your primary backups become exhausted. there may be other options as well. for example, i have a little label maker made by a compary called P-Touch. it takes 6 AA batteries. coincidentally, so does my HT. so i keep the P-Touch whene I keep my AA batteries. i look at the label maker as storage for 6 AA's -- they may not be 100% but it's something. 6) be very careful with "auto-failover" power schemes. auto-failover seems like a good idea. but let me relate to you a little strory. i have a friend who powers his station at home with a big ass DC spply and a big ass Optima deep cycle battery. the two are interconnected via a Powergate (link). this device keeps the battery charged and automatically switches the load to the battery when the AC power fails. when the East coast blackout occured a couple of years ago, my friend was away camping out in PA. like most hams, he has certain equipment which is "always on". in this case, he had a 2M mobile on and a few accessories (powered speaker for his HF rig). well, at the end of his trip he returned home to find a dead battery. his auto-failover scheme had taken control of his available power out of his hands. this example shows that you should keep control over when your backup power is being used. 7) radio operating time on battery power is primarily constrained by TX time -- so keep your transmissions short and keep the RF power output set to the minimum needed for reliable comms. one other factor that can help is by setting the receive duty cycle on the radio. some radio manuals call this "battery saver". this feature reduces power consumption during standy -- effectively increasing the amount of operating time. it works by turning off parts of the receive circuit for a fraction of a second, and then turing these parts back on to check for a valid signal, and then repeating the cycle. during the time these circuits are off (aka sleep mode), the radio needs extremely little power. in Yaesu-HT-speak, this feature is found under "Receive Battery Saver Setup" in your manual. you select how long the receiver circuit is off -- 200ms, 300ms, 500ms, etc. during this time, the radio is fully asleep and the display blinks the "SAVE" icon. as long as your counterpart station transmits for longer than your "sleep" time, you'll hear them. 8) set the APO (automatic power off) function on your battery-operated radio. this way, if you fall asleep or forget that your radio is on, it won't consume all of the available power. on my SHTF HT's i set the APO to 30mins. on my vehicle radio, i set the APO to 1HR. 9) find out the RX power consumption of all of your radios. this is valuable info. put a label on the bottom of the radio or inside the battery compartment with this info. it will help guide how long a given power source will last. a typical HF base station needs about 1.5 to 3A on receive; a typical mobile, about 300 to 500mA on receive, and a typical HT about 150mA (30mA on battery saver standby). hence, if you are on gel-cell battery power it is much better to listen in on the local 2M repeater activities using an HT as compared to a mobile rig. the former will provide more operating time (more than 2x as much) from a given battery capacity. if everything local is down, and you want to listen in on national or world events via shortwave, pick the best HF/SW radio to make use of available power. your hyper-expensive HF rig may have a better front end but if the 10 year old $59 Sony "world band radio" gets the news to you at lower power consumption than that is the better tool for the job. if you have a designed-for-QRP rig (e.g. Icom 703+ or Yaesu FT817), use it in favor of a std HF rig as a SW receiver -- QRP rigs are very much optimized to conserve power (both spec ~300mA receive current). ---
no. as noted previously, the discharge curve is NOT linear. doubling the load does not half the time the battery supports the load -- the battery actually supports the doubled load less than half the time. to wit, from www.trojanbattery.com/Products/ProductSpec.aspx?Name=T-105 we see that the Trojan T-105 has the following characteristics: Capacity Minutes, 447 @ 25A Capacity Minutes, 115 @ 75A so the "apparent capacity" with a 25A load is (447/60) x 25A = 186 AH and the "apparent capacity" with a 75A load is (115/60) x 75A = 143 AH continuing on, we see that the manufacturer also states: 5 Hr Rate, AH = 185 20 Hr Rate, AH = 225. this tells us that the battery will deliver, 185AH/5h = 37A for 5h 225AH/20h = 11.25A for 20h IF the discharge curve were linear, it would show that the battery could supply 4 times the current for 1/4th the time. but, 11.25Ax4=45A and 20h/4=5h. so ideally the battery would put out 45A for 5h. this is not the case; from the manufacturer's data (linked above), the battery can only supply 37A for 5h. putting all of the above into a table, we have a total of 4 datapoints: 11A for 20h (~220AH) 25A for 7.5h (~187AH) 37A for 5h (~185AH) 75A for 1.9h (~142AH) as you can see, the bigger the load, the lower the capacity of the battery. this is just physics, and every lead-acid (wet or gelled electrolyte) battery has a similar characteristic. ps: keep in mind that the T-105 is a 6V battery; you need two connected in series to drive a 12V inverter or to power 12V loads. using two in series does not double the AH capacity, it simply doubles the output voltage. ---
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--- also see www.w4ava.org/races/BatteryFactSheetRev23Jul021.pdf ---
we'll ignore the tuner since it probably draws 500mA only while tuning. .25 x 20.5A = 5.125A avg TX current / hr .75 x 1.5A = 1.125A avg RX current / hr 5.125 + 1.125 = approximately 6.25A per hr of operation is required. from the datasheet, a 9 LB 12V 12AH AGM battery, e.g., www.bb-battery.com/productpages/BP/BP12-12.pdf has the following capacities: 20 hour rate F.V.(1.75V/cell) (600mA to 10.50volts) 12.0 A.H. from the average current we calculated above, we see that the 6.25A falls in between the 5 hour and 1 hour discharge rates. interpolating a little bit, we could assume that at 6.25A, the 12V 12AH rated battery has about 8AH of capacity. 8AH / 6.25A = 1.28 "theoretical" hours of operation. in practice, it will be less due to several factors, one of which should be you -- don't completely discharge a lead-acid battery (wet, gelled, or AGM type). i would use a safety factor or .5, meaning you should double your capacity to get an hour and a quarter of operating time. hence, i would recommend at least a pair of 12V 12A batteries, wired in parallel. better yet would be a pair of 12V 18AH batteries wired in parellel, or a bigger single battery. i would also recommend using as little TX power as possible (this will make a HUGE difference in operating time). ps: and now you you know why QRP rigs are popular for field operations. ---
www.gruberpower.com/gruberpower/advertising/batteries/UPSbatteries/SmallUPSBatt/default.asp www.gruberpower.com/gruberpower/advertising/batteries/UPSbatteries/LargeUPSBatt/ www.gruberpower.com/gruberpower/advertising/Batteries/Batterypacks/apc/ ---
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8 x AA battery pack, from Digi-Key, link. OEM Yaesu E-DC-6 power adapter cable, any online Yaesu store. Andersen Powerpoles, Powerwerx. the nice part about introducing the powerpoles is versatility. while not necessary, they allow you to easily connect the battery pack to anything that needs powering during SHTF.  +  AA battery pack shown close up powering a IC703+   ---  --- and yes, i've just realized that was the worst possible background. thank you.    ---
that 8xAA pack, by itself, is not going to work for the FT7800R. from the 7800 manual:
minimum input voltage, from above spec: 13.8Vdc x 0.85 = 11.73Vdc. maximum output voltage, 8xAA NiMH: 8 x 1.2Vdc = 9.6Vdc. ergo, the 8xAA holder does not produce enough voltage to operate the FT7800R. you need *at least* qty 10 AA cells (=12Vdc when fully charged), and qty 12 would be better (=14.4Vdc when full charged). moreover, AA's have a limited peak current out capability, and even though the radio requires around 0.5A on receive, transmitting even on low power is going to require appreciable current -- which will likely cause the voltage from 12 AA's to sag to a degree that the radio will not operate correctly. for all of the reasons above, i think you will be better off using a small AGM/gel cell battery; for example, a 12V 7.2Ah unit. in contrast to the 12 x AA setup, this type of battery will provide the correct voltage and the peak current capability is far, far greater. --- pre-made version of the AA battery pack pictured above: www.ar15.com/forums/topic.html?b=7&f=126&t=571575 |
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Posted: 8/10/2007 9:55:23 PM EDT
[Last Edit: ar-jedi]
[#19]
communications bug-out-boxes / emergency radios
excellent.
very nice 2M radio.
in essence, yes. but you need to apply some thought to this as well, so that the results are both useful and in line with your expectations. for example, consider the 8 items that i listed at the top of my RACES box writeup:
since you are looking to do something similar but a bit simpler, ask yourself which of these requirements you might change, or even delete entirely. there may be other requirements that you may want to add. the list above is what i thought my box should do at the endpoint, but that list is not necessarily the same as your goals. so take a shot at how your box may differ. this will provide you a good starting point. it's imprtant to know about where you are going before you start out driving. you can certainly make some changes along the way, but there are some upfront considerations that will save you a lot of time and/or money down the road. as an analogy, if your goal was to build a lightweight CQB rifle, the last thing you'd want to start with is a 20" HBAR barrel. that barrel does not help you towards you goal one bit unless you have a lathe and gunsmithing expertise, or you pay someone who does have a lathe and expertise.
from the Yaesu website i found the brochure on the FT1802M. there i learned that the FT1802M has the following current draws:
so we can see that at maximim power out (50W), the FT1802M draws about 10A at 12V. this is a fair amount of power(10A x 12V = 120Watts). i would not recommend that you use the cigarette lighter for this application. the current required by the radio is quite large to be pulling it through the cigarette lighter. while it would appear that installation of the radio into your vehicle would be expedient using the cigarette lighter as the power source, i think you are going to run into a number of problems doing so. for that reason, and several others (electrical noise, primarily), i recommend running the radio power cables directly to the battery (properly fused, of course). if doing so is troubling you, let me know and i will walk you through the proper connections. it is extremely straightforward and can be backed out of if for example your vehicle is leased and needs to be returned without the radio in place. i noted above that the FT1802M draws 10A at 12V, or about 120W. we know that 50W is going out the antenna connector, but where is the other 70W going? the answer is heat. at high output power, your FT1802M chassis is going to get quite warm. the radio housing incorporates fins which transfers heat from the chassis to the surrounding air. through a process called convection, buoyant hot air carries heat away from the radio, drawing in cooler air, and the cycle repeats -- and the radio hopefully stays in it's operating temperature range. however, if the radio is placed inside an enclosure which limits the amount of cool air available, the hot air will just get hotter, and eventually the radio will overheat. mobile radios are quite durable, due to the environment they are designed for (imagine the inside of a car at noon in a hot arizona summer). but whatever enclosure you decide upon, you must make provision for an adaquate supply of cool air. and, that may mean using a fan or other means to move the air along. it all depends on the enclosure, and the amount of time you are planning on operating at high power. at lower power settings, cooling needs will be markedly reduced. --- excellent article on choosing an EMCOMM radio: www.varaces.org/prepare/BestECOMMRadio.pdf --- here is a long article , chock full of little tidbits and interesting viewpoints: "Which HF+ Transceiver is Best for Emergency Use?" www.eham.net/articles/12012 also see "Portable/Mobile Rig for an Emergency" www.eham.net/articles/12100 which starts off with
and see this as well for other angles: "Emergency 'Go Kit' Ideas Needed" www.eham.net/articles/8545 ---- here are some ham porn links of boxed radios: losdos.dyndns.org:8080/public/ham/RACES+ARES-portable-box.html webpages.charter.net/n3ljs/jumpbox.htm home.comcast.net/%7Ebuck0/combox.htm www.wi-aresraces.org/ideas_projects.htm www.larkfield.org/staticpages/index.php?page=20040821182540501 mywebpages.comcast.net/cuti/N1HY/ARES/ <-- very good collection of info! and lists of stuff if you are RACES or ARES inclined: www.tcoe.trinity.k12.ca.us/~tcarc/hlist.html races.org/gokit.htm mywebpages.comcast.net/cuti/N1HY/Go-Kits/index.html <-- good stuff www2.arrl.org/news/features/2003/12/07/1/?nc=1 ---
--- NEW --> EXCELLENT GO-BOX WRITEUP: www.eham.net/articles/17836 ---
homepage.mac.com/clintbradford/PhotoAlbum4.html |
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Posted: 8/10/2007 9:57:58 PM EDT
[Last Edit: ar-jedi]
[#20]
field expedient antennas for SHTF applications www.qsl.net/wb5ude/nvis/index.html www.w0ipl.com/ECom/NVIS/nvis.htm www.tactical-link.com/field_deployed_nvis.htm <-- good practical info! www.vcars.org/tech/NVIS.html www.n2rga.com/double_zepp.html www.races.org/docs/msg008.htm www.cityofseattle.net/acs/newsletters/QRV%20Supplement/ant.htm www.cebik.com/radio.html <-- excellent resource page! www.ac6v.com/antprojects.htm <-- another great page www.fiu.edu/orgs/w4ehw/j-pole.html www.alpharubicon.com/elect/hamtennaswab.htm <-- ham n00bs, these are EASY!!! www.tcoe.trinity.k12.ca.us/~tcarc/hlist.html www.tcoe.trinity.k12.ca.us/~tcarc/htant1.html <-- very nice J-pole plans www.qsl.net/wx2nj/ <-- "ummmm..." ---
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Posted: 8/10/2007 9:59:35 PM EDT
[Last Edit: ar-jedi]
[#21]
DC power connectors / anderson powerpoles The amateur radio community has pretty much standardized on a power connector called the Anderson PowerPole. These clever, asexual connectors are easy to assemble, handle up to 45A, and when paired they prevent reverse polarity mating accidents. Note that there is a PowerPole RED/BLACK orientation convention in widespread use within the amateur radio community, and adherence to proper crimping is essential.    Anderson PowerPole web page www.andersonpower.com/products/standard-powerpole.html Anderson PowerPoles are available from www.powerwerx.com/ www.westmountainradio.com/ RACES writeup www.races.net/powerpole.phtml See also pages.ripco.net/%7Eormos/sarc-ema-andersonpowerpole.html and www.westmountainradio.com/supportrr.htm and www.qsl.net/w6apd/powerpole.html and home.comcast.net/~buck0/app.htm --- Reccomended "Starter Kits" for the powerpole, here are "set kits" -- everything you need to terminate 10 power connections: 15 Amp Red/Black Anderson Powerpole Sets Recommended for use with 16-18 gauge wire www.powerwerx.com/product.asp?ProdID=3015&CtgID=3014 30 Amp Red/Black Anderson Powerpole Sets Recommended for use with 14-12 gauge wire www.powerwerx.com/product.asp?ProdID=3016&CtgID=3014 the 15A and 30A connectors will mate no problem. the only difference is the diameter of the hole in the actual contact. the smaller one is designed for the lighter 16-18 guage wire, and the larger one is designed for the heavier 14-12 guage wire. both contacts can either be crimped or soldered on. in an HT application, the 15A version will be fine. for a mobile application, get the 30A contacts. ---
you don't really have to "choose" per se. the plastic housings for all three of your listed sizes are the same; the only difference is the metal contact rating. look closely at the pic below -- one contact is a 15A (left) and the other is 30A (right). they both fit into the same pair of plastic housings. i use the 15A contact size for smaller diameter wire (such as 16-18AWG) and the 30A contact size for larger diameter wire (such as 10-14AWG). losdos.dyndns.org:8080/public/ham/powerpole/DSCN3275_sm.jpg see for example, www.powerwerx.com/anderson-powerpoles-accessories/anderson-powerpole-sb-series-sets/
note that where the individual pieces are sold, www.powerwerx.com/anderson-powerpoles-accessories/individual-housings-contacts-roll-pins/ you see you can get the 15/30/45A housings in different colors, www.powerwerx.com/product.asp?ProdID=3662&CtgID=1020 and you can get the three different sizes of contacts to fit the above housings, www.powerwerx.com/product.asp?ProdID=1659&CtgID=1020 www.powerwerx.com/product.asp?ProdID=1325&CtgID=1020 www.powerwerx.com/product.asp?ProdID=1660&CtgID=1020 however, it is generally more economical to buy the 10 or 25 piece "sets" which include the red/black plastic housings and the metal contacts. the most popular size Powerpole is the 30A type, which covers about 99% of everything you'll ever need to do with ham radio. that said, i ordered some extra 15A contacts at the same time as buying a 25pc 30A set -- i use the smaller 15A contacts when connectorizing those 6xAA battery holders and similar low current, small diameter wire applications. |
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Posted: 8/10/2007 10:02:03 PM EDT
[Last Edit: ar-jedi]
[#22]
RACES/ARES -- amateur radio emergency communications RACES/ARES web sites: www.races.net/ www.races.net/links.html www.ares.org/ --- handout from my RACES org, originally done by the VA RACES folks, some good info even for novices and pros alike... (1.4MB PDF) losdos.dyndns.org:8080/public/shtf/ACSSurvivalSkillsUburban.pdf the original in microsoft powerpoint format is here: www.w4ava.org/races/KKauxcomm33.htm also check out some of the info on this page, more VERY USEFUL stuff: www.w4ava.org/races/MMauxcomm42.htm ps: if you do nothing with the above PDF but give it to someone you know, i think we'll all be better off... --- ARRL Emergency Communications Handbook www.arrl.org/catalog/?item=9388 ARRL Emergency Power for Radio Communications www.arrl.org/catalog/?item=9531 Dave Ingram's Guide to Emergency Survival Communications www.amazon.com/exec/obidos/tg/detail/-/0916661059?v=glance --- i do have one comment here. i don't own any of the above books but i caution you as follows: many "amateur radio emergency operations" texts have chapter upon chapter of information related to message handling (e.g. NTS). this is the "formal" part of amateur radio communications which includes standardized processes, procedures, and forms related to accurate interchange of information between two operators. it is critical in an emergency situation (e.g. Katrina) that things be done in a somewhat organized manner so that the right people receive the right info in a timely fashion. in general, this whole art is called "traffic handling", and a well trained, experienced set of folks on an emergency net can move a lot of data accurately and quickly using these methods. here is the standardized form: www.arrl.org/FandES/field/forms/radiogram2.pdf moreover, a large part of emargency communications is regarding interaction with the "served agency" -- which may be the Red Cross, FEMA, your local police, or similar. as an example, RACES operators may be colocated in a trailer with FEMA and other disaster relief personnel. should ham radio be the only communications path in and out of the affected area, the RACES operator(s) will become focal points. if so, what you convey over amateur radio frequencies has to be carefully controlled, who you distribute that info to has to be carefully controlled, and so on. my point here is that "emergency communications" in amateur radio context is not just about using a battery and a piece of wire; it's a whole ball of wax. those of you ln law enforcement know what ICS is; the same system and hiearchy is used in amateur radio emergency comms. that said, only a few folks here may get involved with RACES, ARES, SATERN, SKYWARN, or similar -- and therefore the chapters on traffic handling and agency interaction may be interesting but for the large majority of you this info will not be as useful as actual techniques for remote operation, construction of field expedient antennas, and using/monitoring battery power. for this reason i encourage you to review the table of contents prior to purchasing a book on "Emergency Communications", so that you get the technical info you are looking for rather than a lengthy discourse on traffic handling/messaging. see also this forum www.eham.net/forums/EmergencyCommunications ---
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Posted: 8/10/2007 10:26:28 PM EDT
[Last Edit: ar-jedi]
[#23]
EMP and ham radio (ack!)
there are so many factors which affect this question that it is nearly impossible to say, with any certainty, whether a given device will continue to function post-NEMP. as i wrote some time ago here in the SF, archive.ar15.com/forums/topic.html?b=1&f=123&t=521338&page=3
that said, in all likelihood, most all portable, battery operated, handheld devices (such as ham HT's, geiger counters, and the like) will not be affected by EMP. the distance-reduced field intensity and the minimal capture area will prevent any permanent damage, although there may be minor transient issues. here is what an ARRL report on the EMP effects to ham radios says:  as you can see, as long as there are no long power cables or antennas connected to the device, it should survive an EMP. ---
ok, i am going to try to make this as simple as possible. however, i'm quite sure my simplification will result in AR15.com going down from the massive number of "corrections" offered by my peers. but let me attempt it anyway in nice, easy, practical terms. let's start with something you know, an FM car radio. but first we have to start at the source, the FM radio station. the transmitter at your favorite station takes an audio signal (say from a CD player) and modulates it onto an RF (radio frequency) carrier at a frequency of say 100 MHz. modulate, in case you were wondering, in this context means that the input audio changes very slightly the output frequency that the radio station is transmitting on. you can read more on how FM (frequency modulation) works via google -- i can't explain it to you here without typing for 10 more minutes. thousands of watts of RF are sent up a piece of coax into an antenna -- where that power is radiated as an electromagnetic wave. for our purposes, we can use a lightbulb for an analogy -- there electrical power gets turned into visible light, which is a type of electromagnetic energy. an electromagnetic wave carries with it energy, just as a wave of water on the ocean carries with it kinetic energy. this EM energy, as you will see in a moment, is what makes all this radio stuff happen. the EM wave that you are most familiar with is in your kitchen: EM waves in what is called the microwave region bombard whatever is placed in the appliance, rapidly spinning the boomerang shaped water molecules. this creates a lot of friction, which then produces heat -- as anyone who has used a belt sander knows. so you see, strong EM fields can boil water! so back at our FM station, EM waves "spring" from the transmitter's antenna, radiating in all directions. btw, the strength of these waves decay as the square of the distance, and therefore are quite weak after a trip of many miles. at your car, a long metal rod is used to capture these waves. the EM waves that impinge on the antenna create a very tiny varying current along the surface, and a very sensitive circuit built into the radio detects this current. that current is changed into a small voltage, and then amplified, and fed into another circuit which ultimately delivers the low frequency audio back to an audio amplifier and finally to a set of speakers. the voltage seen by the radio at the antenna input is on the order of 10's of microvolts (millionths of a volt). the circuits are thus very sensitve and correspondinly quite delicate. moreover, even if the power to the radio is off these circuits still lie in the path of the applied voltage. suppose, instead of a very weak EM wave being captured by the antenna, a strong EM wave is. what do think the effects might be? what if the EM wave is so strong that the sensitive circuit is not able to cope with the applied voltage? the answer is that the delicate transistors used in these circuits will fail, usually because of thermal reasons (tiny conductors fusing open) or a situation called dielectric breakdown (translated: insulator punch-through). what is going on inside a transistor's tiny body is conceptually no different that what is going on inside the hydraulics of a tractor. apply too much pressure (=voltage) or too high of a flow rate (=current) somewhere in the system and there will be a pop. --- i have described how an FM radio with an exposed antenna might be susceptible to fail if the passing EM wave carries enough energy. the fact is that ANY exposed metal captures these same currents/voltages from EM waves. your house gutter, for example, at this very moment is receiving the Voice of America shortwave station. that energy goes nowhere, but suppose we take another example. your ADSL or cable modem sits on the end of a very long piece of wire (that's our antenna). a very strong passing EM wave can either temporarily interrupt (bit errors) or permanently damage (blown receiver) these devices. it will be useful for you to know that a lightning strike, besides the immediately visible bolt, produces a very strong EM wave that can damage equipment quite far from the actual strike point. a toaster over, per your comment above, has no delicate circuits like a PC or radio both have. a toaster oven is basically a big resistor designed to get hot, sucking down 1000 to 1500W in the process. a radio is not designed for this! any delicate circuit with long wires attached it can be affected by strong EM waves like the type produced by a nuclear EMP. how the equipment reacts is a function of dozens of factors, including how strong the EM field is, how long the attached wires are, how robust the circuit design is, and so and so forth. thus there is no way to answer the question, "will X be affected by an EMP?". --- additional reading material: en.wikipedia.org/wiki/Electromagnetic_pulse www.twq.com/07autumn/docs/07autumn_cmp.pdf www.domprep.com/legacy/dpjournal/DPJournal0607.pdf cisac.stanford.edu/publications/day_after_action_in_the_24_hours_following_a_nuclear_blast_the/ |
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Posted: 8/10/2007 10:30:29 PM EDT
[Last Edit: ar-jedi]
[#24]
constructing a J-pole antenna for VHF/UHF
the VX-170, like most current HT's, uses an SMA connector. the SMA has excellent RF characteristics, but less than stellar mechanical strength. the problem you are facing is that the antenna shroud completely encloses the male end of the SMA, and in turn when the antenna is attached to the radio the shroud mates intimately with the VX-170 housing, assuring a waterproof connection. you should not need a counterpoise with the OEM antenna, but trying it can't hurt. offhand, though, i can't think of a good way to attach the counterpoise without possibly reducing the water resistance at the same time.
any length of more than about 3' should be ok. i have about 7-8' attached to my J-poles, and that seems to work out just fine. you can of course go longer as needed. i routinely use a 15' "extension cord" with my J-poles, vis-a-vis a BNC barrel connector and a 15' piece of RG58 with male BNC's on both ends. now then, in theory the J-pole is a balanced antenna and you are feeding it with unbalanced line. in theory you would need a balun for this antenna. in practice, the unbal-balanced transition does not cause issues, especially at the power levels output from an HT. i would not dump 100W into a J-pole without a little more engineering work, though. if you find you have feedline current, make a 4" dia loop of 4 turns of the feedline coax, and you will be all set. see below for an example: home.comcast.net/~buck0/llcoolj2.jpg attaching the coax to the 300ohm twinlead is pretty straightforward. first -- only strip back the minimum amount of coax; you should have less than 1/4" of exposed center conductor and about the same amount of braid. twist the braid such that all of it comes to one side of the coax. lay the prep'd coax in line with where you made the connection cuts on the twinlead. now solder the center conductor to the long leg, and the coax to the shorter leg. now you can use heatshrink or electrical tape to wrap everything up. note: if, when you twist the coax, you can cause the center conductor to short to the braid, you have too much of each. pare back the two and try again. the picture attached below is of a design using 450ohm ladder line, so the dimensions are a little distorted compared to your 300ohm TV lead -- but the method of attachment of the coax is exactly the same. keep the coax leads short, and run the coax parallel with the "base" of the J-pole. home.comcast.net/~buck0/llcoolj1.jpg ps to others considering the J-pole: see www.dxzone.com/catalog/Antennas/J-Pole/ www.arrl.org/tis/info/pdf/0302038.pdf home.comcast.net/~buck0/ll_coolj.html (the pictures above come from here) www.bloomington.in.us/~wh2t/Jpole.htm www.eham.net/reviews/products/37 www.bloomington.in.us/~wh2t/Jpole_files/hamtenna1.gif www.vcars.org/tech/Image9.gif pps: for base use, i recommend the Diamond X50. the price is right and the performance can not be beat. it is physically unobtrusive as well. huge value for what you get. www.eham.net/reviews/detail/1054 ---
some antenna designs will appear to be a short at DC or a complete open. it depends on the design of the antenna and also the arrangement of the elements. for example, the popular DIY J-pole is a DC short. i know that it's sometimes tough to get your mind around, but RF and DC do different things. an inductor, for example, is a dead short to DC. but at a high enough frequency, RF will not pass through an inductor. the reverse situation is true for capacitors: DC open, but a high enough frequency signal will pass. |
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Posted: 8/10/2007 10:31:00 PM EDT
[Last Edit: ar-jedi]
[#25]
coaxial cable selection (impedance and loss) I'm just a little confused on soldering the female BNC connector to the end of the coax.
where did you get the BNC from? is it an Amphenol/AMP type part with a bunch of separate components, or is it a "screw on" type which twists onto the cable? Also, the only coax I could find locally was RGU6 (not sure of the letters as I'm at work and can't check). The package said it was 75 Ohm resistance. Will this work or do I need to order some other kind from gigaparts?
hard stop here. you need 50ohm coax or you will never get the SWR down below 1:1.5 or so. a 50ohm impedance coax like RG58 type (and all the derivatives like RG58AU, RG58U, etc are ok) is needed for your ham projects. you can probably pick up some RG58 at your radio shack. note that you will need BNC's suited for RG58; i don't know what you have right now. RS carries "instant-on" twist type BNC's which don't need soldering. i would not recommend them for high power or outside use, but they work pretty well for J-pole type projects. basically you strip the coax per the directions on the back, and screw the connector onto the coax. see the upper right of the pic below. losdos.dyndns.org:8080/public/ham/races-box/construction/DSCN1070_sm.jpg ps: in general: 75ohm coax for VIDEO applications (cable TV, sat TV) / 50ohm coax for RADIO applications (ham). of the 1/4" dia coax types: RG59 = 75ohm impedance RG58 = 50ohm impedance ––- coax loss calculator: www.ocarc.ca/coax.htm –––– Originally Posted By uscombatdiver:
His explanation lacks enough information on this. luckily there is this new thing called the Internet. start here, http://en.wikipedia.org/wiki/Transmission_line then go here, http://en.wikipedia.org/wiki/Coaxial_cable Originally Posted By uscombatdiver:
We used all sorts of different coax without particular impedance when I did towers and the antenna was still matched to the radio. there are two common impedances for coaxial cable used in modern RF applications, 50 and 75 ohms. the reasons for this are historical and revolve around striking a balance between power handling, antenna matching, and attenuation –– with 50 ohm impedance corresponding well to the drive impedance of a half wave dipole antenna in real environments, and 75 ohm impedance having less attenuation when used for long runs. any modern radio communications device (including associated test gear, e.g. spectrum analyzers etc) will have 50 ohm impedance unbalanced inputs (e.g., receiver) and 50 ohm unbalanced outputs (e.g., transmitter) and therefore use 50 ohm impedance coax (e.g RG58, 9913/LMR400, etc) and 50 ohm impedance connectors (e.g 50 ohm BNC, N, SMA, etc). similarly, since CATV systems have very low level signals and are benefactors of low attenuation for long coax runs, 75 ohm coax is used. examples of such are RG59 and RG6, plus several types of hardline used for headend to community distribution (pole-to-pole) applications in the CATV industry. the connectors used for termination in the CATV industry range from true 75 ohm impedance weatherproof types used on hardline to the ultra-cheap and ubiquitous "F" connector used for in-house distribution and on the back of set-top boxes. n.b. in some applications, low loss 75ohm CATV coax or hardline can be employed in radio applications by using quarter wave matching stubs (or the discrete equivalent) at the transitions. for example, if a long "scrap" of 75 ohm impedance CATV hardline is surplussed by a local cable TV operator, an amateur radio club could employ it for use on a tall repeater tower –– less attenuation of the received signal is the primary benefit. again, matching sections are required to connect the nominal 50 ohm impedance radio equipment (specifically the duplexer) and 50 ohm impedance antenna to the 75 ohm impedance hardline which joins the two. that said, if as you stated you were employed erecting radio towers for cellular or two-way radio applications, the coax or hardline you were installing was 50 ohm impedance (such as Andrew/Commscope Heliax), and the connectors you were using were 50 ohm impedance (such as type N or type 7-16 DIN) . the coax may have come in many different sizes and construction types but the characteristic impedance was 50 ohms. Originally Posted By uscombatdiver:
I guess I will need to hit the antenna theory book hard when it gets here (it's been over 10 years since my tower days but I'm not completely void of any memory of it).  the antenna is just another bump in the impedance graph of a very long transmission line. 
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Posted: 8/10/2007 10:31:51 PM EDT
[Last Edit: ar-jedi]
[#26]
amateur radio bandplans www.arrl.org/FandES/field/regulations/bandplan.html www.arrl.org/FandES/field/regulations/bands.html www.arrl.org/FandES/field/regulations/Hambands_color.pdf VHF/UHF: www.icomamerica.com/en/support/kb/Article.aspx?Download=1919 <-- PDF HF: www.icomamerica.com/en/support/kb/Article.aspx?Download=1920 <-- PDF www.dxzone.com/catalog/Ham_Radio/Band_Plans/ |
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Posted: 8/11/2007 1:32:04 AM EDT
[Last Edit: ar-jedi]
[#27]
NVIS –– Near Vertical Incident Skywave: a technique for short range HF communications hometown.aol.com/alonestaryank/NVISKIT.html www.tactical-link.com/field_deployed_nvis.htm www.qsl.net/wb5ude/nvis/ www.w0ipl.com/ECom/NVIS/nvis.htm Originally Posted By ThePrepared_com:
There is NVIS info spread through a couple threads so I thought I would try to bring the entire NVIS thing into this thread. I believe NVIS is a highly important part of survival communications. NVIS allows you to reach stations 0-300 miles away that would otherwise be missed in the skip using other methods. In my opinion you are better off being able to communicate with close communities who are able to respond quickly. What is NVIS (Near Vertical Incidence Skywave)? (From TacticalLink.com) NVIS , short for Near Vertical Incidence Skywave, utilizes high-angle skywave paths between stations instead of ground-wave or surface-wave in order to communicate via HF radio. NVIS was originally evaluated by U.S. Army Forces in Thailand during the Vietnam conflict in the mid-1960's It was found that Mobile stations, using whip antennas bent parallel to the ground, could communicate more reliably with their base-stations. Signal strengths would be weaker using high-angle skywave but communications would be more reliable, less subject to fading, and consistent between stations. This was because the intervening terrain was less of an absorber of signals. Terrain obstructions between stations, such as hills, mountainous areas, jungle growth, built-up areas with tall buildings, no longer become path obstructions with stations when NVIS techniques are employed.
NVIS Links NVIS Propagation Conditions hflink.com/propagation/ ARRL Power Point Presentation on NVIS (Great place to start looking for information) www.arrl.org/FandES/ead/materials/NVIS.ppt ARRL Doc File on NVIS Operation arrl-sc.org/Tech%20Presentations/Near%20Vertical%20Incidence%20Sky%20Wave.doc Hi-Q NVIS Antennas www.hiqantennas.com/ Field Deployment of NVIS (Actual setups and tests in the field) www.tactical-link.com/field_deployed_nvis.htm Elpa Antennas (No longer sold new but can be found from surplus resellers. Specifically made for NVIS) www.hflink.com/antenna/elpa/ Originally Posted By Gamma762:
www.athensarc.org/nvis.asp Originally Posted By pcsutton:
I have an IC-7000 with an HI-Q 5/80 vertical on my truck. The antenna has a 102" whip on top. I tie the top of the whip down to my trailer hitch so it doesn't hit stuff and behold.....it works GREAT as an NVIS antenna. If I want to DX...I just untie the bottom of the tether and allow the whip to stand straight up. Just talked to a guy in Jamaica from Ft Worth yesterday. Not bad for a mobile, given the solar cycle. NVIS from Army MARS: NVIS in Depth Quick & Easy NVIS Originally Posted By Gamma762:
http://www.signal.army.mil/ocos/ac/articles/fiedler/dfnjarng.pdf |
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Posted: 8/11/2007 2:02:53 AM EDT
[Last Edit: ar-jedi]
[#28]
listening to public service and shortwave freqs using ham equipment Originally Posted By KS_Physicist:
Originally Posted By Nolan1964:
With a 2m mobile like yours jedi, could I listen to (118.000 MHz - 136.975 MHz) the aviation freqs? The first question's answer depends on the radio you're talking about. Most modern radios do have "extended receive" where you could hear aircraft through public service. Some older ones (and perhaps some new ones, I don't know) were restricted to receive on transmit frequency only. This specification (receive range) is prominently displayed, often right in the ads. let me clarify one thing here though. the ability to tune to a given frequency has to be matched by the ability to demodulate the signal you are looking for. in the example case, aviation band frequencies are AM, and not all HT's/mobiles have an AM mode. my Yaesu VX6R does, and thus i can tune in and listen on aviation frequencies using that radio. however this is not the case with the V8000 (my mobile) and the VX170 (one of my HT's). they are spec'd fpr RX from 137MHz to 174MHz, FM mode only. hence, there is no air band RX possible on either rig –– you can't tune there nor can you set AM mode. the Yaesu FT8800 (a popular dual band/dual receive mobile) will do AM across the full RX range, which will allow you to RX commercial aviation traffic as well as listen in on the "milair" frequencies in the 200-400MHz range. ––- Correct me if I'm wrong but I'm thinking this might be useful if SHTF. I know little about them except a buddy of mine had one in school and we never had a party interrupted by unwanted guests (police). I saw some Uniden 100ch and 200ch with very small price difference is 100 channels fine or go for more?
buying a scanner based solely on how many channels it has is roughly equivalent to buying a gun based on how many rounds the magazine holds. IMHO the total number of memories is one of the least important parameters. more important: - trunking capability. (*) - analog vs. digital decoding. (*) - frequency range. - scanning rate. - 12dB SINAD sensitivity. - adjacent channel selectivity. - auto-memory assignment. - PC interface. - power consumption while scanning. (*) before you buy ANY scanner, find out what type of radio system(s) your local municipality uses. ––> www.radioreference.com/modules.php?name=RR the radio system in your town could be an "old fashioned" analog narrowband FM system in the 150MHz range (VHF) or in the 460MHz range (UHF). these are the simplest to monitor; any garden variety scanner should work ok as will almost any 2m/70cm ham radio. but, your local police/ems/fire could be using the latest gear, which may mean P25/APCO-25 digital radios combined with channel trunking. in this case, you need a more expensive, more capable scanner which can interpret the digitial signals and track the trunking channel changes. there is no way to half-ass this –– you will get absolutely nothing without complete capabilities on the scanner. finally, if your local public safey folks have enabled encryption on their digital sets, you are probably SOL unless one of the local brainiacs has either cracked the key (highly unlikely) or it was leaked from the department radio technicians. ––- Originally Posted By aaron_fsp:
An HF ham transceiver usually has a general coverage receiver and can receive SW broadcasts, SW broadcasts/utilities, etc. www.primetimeshortwave.com/america.txt tf.nist.gov/timefreq/general/pdf/1383.pdf tf.nist.gov/timefreq/stations/wwv-wheel.htm ––- Originally Posted By aaron_fsp:
www.mediamax.com/aaron_fsp/Hosted/shack.txt ––- Originally Posted By NUCdt04:
I was looking at a radio like the Yaesu VR-5000 Linkey I like this radio because of the fact that it covers all the way up to almost 2600MHz. I also like the option to use it like a scanner for the surrounding areas. I work in my company intel cell and also help out with comm around here so I can grab a terp real quick if I pick up anything that sounds interesting. The one sold through HRO shows it's only cell blocked (as opposed to other models that require govt authorization- which I may be able to pull off, there is GSM cell coverage in the area). Are there other radios out there that have comperable (or better) coverage and are not cell blocked back in the dawn of mobile phones, the cell networks employed a technology called AMPS: the Analog Mobile Phone System. with a scanner capable of demodulating NB FM signals in the 800-900MHz band, one could listen in on phone conversations carried on AMPS networks. basically, you "snooped" the signal from the cell site to the handset using the scanner; in some cases this only gave you one side of the conversation, depending on how the nearby AMPS cell site was configured (the other side of the conversation was carried on a different frequency). our gov't got involved (what else is new), and made it illegal to offer for sale a receiver that could tune in the cellular band. hence the "hole" in the frequency tuning range of receivers such as the one you linked to above. not too long thereafter, use of digital cellular protocols became prevalent. you may have heard acronyms like CDMA, PCS, GSM, and so on. in these schemes, your voice is digitized (converted to 1's and 0's) in the handset, and sent as data to the cell site. the advantages of doing this are many-fold, including reduced power consumption of the handset (leading to longer battery life), better immunity to multipath and other transmission impairments (no more static), and the ability to subcode other data (like text messages). one other important advantage of a digital signal is that it makes snooping much more difficult –– approaching impossible for "casual eavesdroppers" without significant financial and technical resources. i'm telling you all this because unless you local mobile phone operator is using mid-1980's cellular equipment, you are not going to be listening to any cellular conversations. a CDMA, PCS, or GSM signal sounds like white noise on an FM receiver, and the frequency-hopping nature makes it impossible to follow anyway. summary: today, there is no benefit to having FM-only reception in the cellular bands. Originally Posted By NUCdt04:
We have pretty crappy power here... Ok won't lie the power here sucks. The generators are beat to death from the heat and constant running- plus a high load always on them. There are sometimes brown outs and small surges- I need a way to keep the radio protected from that. Also I'm guessing that I need a seperate power supply- do they have ones rated up to 240V? I have 120 in my room also but have an empty line on the 240 side- would rather use that if possible. like most amateur radios, the VR-5000 operates off of 12Vdc, in this case drawing a scant 0.7A (700mA). if you are concerned with the cleanliness of your power, you can power the radio all day (and then some) with a car battery placed outside your domicile with some wires running though the window. overnight you can attach an small, inexpensive battery charger (BatteryTender Jr, or similar) to replenish the electrons. or you can simply take the battery over to the motor pool (or similar) once a month, and put it on a bigger charger for a day. one benefit of using a battery is that it guarantees that the noise floor of the receiver is at a minimum. Originally Posted By NUCdt04:
Antennas..... I was thinking a horizontal long wire for the HF side because I can run some coax out my sandbagged up window to the roof and across to the roof of a post- what about VHF and up side of the radio? I'm guessing a vertical on the roof also- I can get away with it no problem but I'm trying to keep this in my budget- I can't start going crazy with beam antennas- plus there is no place to put them and I'd get some funny questions. for < 30MHZ, a horizontal wire antenna such as the G5RV is one suggestion. what say all you HF'ers? help this man out! for VHF, see if you can find a local plumber and about 10 feet of copper pipe. we can set you up with a J-pole of some configuration. on the other hand, your situation is RX-only, so almost any vertical element with a good match to your frequencies of interest will work. –– Originally Posted By Wolfcri:
I am not sure if the local police use digital radios or if that even matters... or what else this thing will receive. you have a very useful scanner, suitable for receiving analog FM signals. 1st –– you can get NOAA weather radio on one of 7 local frequencies. you will have to try each to see which is strongest. see the bottom of this link, the frequencies are in a horizontal table, all around 162.5MHz: http://www.nws.noaa.gov/nwr/ 2nd –– you *may* be able to receive the local police/sheriff/fire/ems/etc in either the VHF band (approximately around 155MHZ) or in the UHF band (around 460MHz). as noted above, your local public safety folks may have moved on to a digital system, in which case you are SOL. see http://www.radioreference.com/apps/db/ 3rd –– you can monitor amateur (ham) radio frequencies in the 144-148MHz, and the 440-450MHz range. you can find the frequencies of amateur radio repeaters in your area via http://www.ar15.com/forums/topic.html?b=10&f=22&t=604477#10323243 there are others but that should get you started. |
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Posted: 8/11/2007 2:25:25 AM EDT
[Last Edit: ar-jedi]
[#29]
soldering, general and RF connectors
--- for your electrical projects, you will need two types of irons. the reason you need two is the same reason you need different types of guns -- different purposes = different tools. for "electronics" type soldering, meaning kit projects or repairs on relatively delicate equipment or with small dia wire (18 AWG or thinner), you should use a "pencil" type iron. typically the better ones have a base and then a pencil wand. interchangable tips allow you to pick a tip to suit the job. better bases have temperature controls built into them to hold the iron at a suitable temperature. below, in the upper right hand corner, you see my Weller pencil iron, with the thermostat on the base. as you can see, i am working on a somewhat delicate project, which is what this iron is designed for. with this type of iron, you can easily and safely work on both through-hole (TH) and surface mount technology (SMT) electronic components. the pencil iron's attributes are light weight, relatively low power, and carefully controlled tip temperature. losdos.dyndns.org:8080/public/ham/PocketTracker/DSCN1172_sm.jpg losdos.dyndns.org:8080/public/ham/PocketTracker/DSCN1150_sm.jpg the type of iron shown above, however, is not suited for soldering PL259/UHF connectors or similar larger jobs. the PL259/UHF connector requires soldering the coax braid to the connector housing, and the tip mass of the smaller irons is usually insufficient to generate enough heat to properly solder the braid. explanation: the long metallic coax braid and the connector housing conspire to "wick" the heat away from where you are trying to solder, leading to a cold solder joint. you may have experienced the same problem when using a std issue propane torch to solder (sweat) large diameter [1" and above] copper water pipes together -- the heat is transferred away so quickly that you can't get the joint hot enough to get good solder adhesion. note also that BNC, SMA, and N connectors use a different coax attachment scheme and can be reliably soldered with a low power iron. these three connectors do not require soldering the braid to the connector housing; instead, the braid is mechanically clamped by a threaded ferrule. ------------- so what to use for larger jobs, like the PL259/UHF connector, and for larger dia wires (14 AWG and heavier)? this problem can be solved with an iron with more mass at the tip and the ability to supply more heat to the tip. typically this means an old-fashioned pistol grip iron, 100W or so. however, for the past few years i have been using an EXCELLENT butane-powered iron and have found it to be extremely versitile. it will solder PL259/UHF connectors on, and also do relatively delicate work as well. moreover, the soldering tip can be removed and replaced with a hot air attachment for collapsing heat-shrink tubing. i heartily recommend the Weller Portasol, it has proven to be very useful for many projects. for pics of the Portasol. see losdos.dyndns.org:8080/public/weller-portasol/ -- see also this excellent series of tutorials... www.tangentsoft.net/elec/movies/ |
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Posted: 8/11/2007 2:45:47 AM EDT
[Last Edit: ar-jedi]
[#30]
ham radio and the interweb -- perfect together
here is a start: APRS: a means for position discovery and distribution using RF and the internet... using a generic GPS attached to your radio, other amateur radio operators can track your movement using a web browser. in addition, data from automated weather stations and such are included as well. en.wikipedia.org/wiki/Automatic_Position_Reporting_System www.aprs.org/ www.openaprs.net/ <--- check it out, APRS data on Google Earth maps www.findu.com/ Packet Radio: TCP/IP over RF, with gateways between RF and the internet... this is infrastructure, not an application itself. it is possible to send SMTP email, for example, using packet radio. en.wikipedia.org/wiki/Packet_radio en.wikipedia.org/wiki/AMPRNet WinLink: send email from anywhere in the world etc using an HF radio... sort of self-explanatory, but note that it is in widespread use by mariners and and government agencies. en.wikipedia.org/wiki/Winlink www.winlink.org/ Echolink: VoIP (voice over IP) for amateur radio operators; interconnects via the internet and RF... using a PC, you can talk to other Echolink-connected hams, and also with Echolink-enabled repeaters. en.wikipedia.org/wiki/Echolink IRLP: internet radio linking project, connects repeaters using internet TCP/IP links... repeaters in distant geographic areas can be dynamically linked to create ad-hoc communities en.wikipedia.org/wiki/Internet_Radio_Linking_Project Hinternet: the implementation of wireless data networks over amateur radio frequencies using commercial off-the-shelf (COTS) hardware such as 802.11 access points and D-Star equipment. en.wikipedia.org/wiki/Hinternet DSTAR: a digital radio standard with features to interconnect with the internet en.wikipedia.org/wiki/D-Star ---
a PC, an internet connection, a microphone, and a speaker. PLUS A VALID CALLSIGN.
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Posted: 8/11/2007 2:46:42 AM EDT
[Last Edit: ar-jedi]
[#31]
APRS - automated position reporting system
get an older 5W HT. the duty cycle on APRS is low, so the finals won't cook. if you are using a TinyTrak3 you can set it up to ping once every 2mins or 5mins or so. the APRS message is about 1 second in length, so this will not be a problem whatsoever with the HT -- even in a hot car. the other reason you don't want to run more power is that you'll be heard by many relay stations. while this may sound like a good thing, it's not. ps: btw to all... this is the canonical site for APRS info www.ew.usna.edu/~bruninga/aprs.html ar-jedi |
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Posted: 8/11/2007 2:55:11 AM EDT
[Last Edit: ar-jedi]
[#32]
using amateur radios for transmitting on commercial or public safety frequencies a.k.a. legalities and related regulatory issues
the above is completely incorrect and is in fact unlawful. your amateur HT is not FCC type-accepted for use on public service frequencies. hence, you can not legally operate an amateur HT outside of amateur frequencies. a quick google will show you a recent case where a firefighter thought it would be "handy" to use an amateur HT on public service freguencies, namely his department's. the FCC was not amused and he and his chief were fined
i hope you are not involved in an incident where folks end up investigating why you were not using your issued duty radio and instead were relying on another piece of gear which was neither designed for the task nor type-certified by the FCC for use on public safety frequencies. ETA: www.qrz.com/download/main/mods.html
---
no -- you are still in the wrong. the assumption underlying that question and the corresponding answer is that a modified amateur radio is the only available means of communication in a life or death emergency. that is, the FCC rule is intended to allow the person bleeding out/trapped/lost/freezing/whatever the ability to communicate with rescuers using any means possible. this is not the case if you, as a SAR responder, were issued a radio and you are part of a search and rescue operation. you are not the party in a life an death situtation. while an amateur HT may be used to communicate on amateur frequencies with the party in distress, communicating with your peers on public service frequencies must be with the radio you were issued. --- www.arrl.org/news/enforcement_logs/2002/1019.html
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---
no. amateur radio rules prohibit intentional encryption of transmissions. there are, however, legal methods of operation which enhance obfuscation. one example, use split mode operation. the TX and RX frequencies are different, and therefore a casual eavesdropper would have a tough time finding and then tracking the conversation. second example, use low TX power and high gain directional antennas. reception off to the sides and to the rear will be difficult. ---
true. very true. the problem with this approach is that it does not afford you any legal opportunity to learn, practice, and hone your skills. it's sort of like saying that the local PD/state police/FBI/ATF won't care who is CCW if SHTF so you should not bother getting a CCW permit, getting some training, learning your strengths and weaknesses, and practicing a million and one skills so when SHTF does happen you won't be carrying your Glock Mexican style ready to blow your nuts off. it's so easy and lazy to say "gov't agency XXXX won't care if YYYY happens, so i'll just worry about ZZZZ then." i, for one, would like to have my skillsets in place prior to SHTF, so i don't have to "learn on the job" while my family and i are in danger. you may choose to disagree. |
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Posted: 8/11/2007 3:04:33 AM EDT
[Last Edit: ar-jedi]
[#33]
using commercial, FCC type-accepted radios for transmitting on amateur bands it is perfectly legal to use retuned commercial equipment on amateur radio frequencies. many hams retask surplus Motorola and GE public safety radios into amateur repeaters in the 6m, 2m, and 70cm bands. other folks use rugged Motorola and Vertex/Standard HT's for amateur uses as well. one benefit is that that these radios can continue to be used on public service frequencies -- good for first responders who also happen to be hams. one drawback is that most commerical radios are not front-panel programmable. in other words, a PC, some specialized SW, and an interface cable must be used to program memory locations before use. other commercial/industrial radios can be adopted for amateur use as well. here is one example -- an inexpensive Standard Horizon marine radio that is PC-programmable for amateur frequencies, and comes as a kit with lots of nice accessories that happen to be form/fit/function compatible with the Yaesu VX170. store.marine-radio-store.com/sthohxvhfham1.html
--
(1) radio purchase info is one page back, e.g. www.marine-electronics-unlimited.com/Standard+Horizon+HX370.html and more generally www.google.com/products?q=HX370S&btnG=Search+Products (note: you *probably* don't need the more expensive Intrinsically Safe model [HX370SAS] as this model is specifically designed and individually tested to ensure that operation does not ignite nearby flammable vapors) (2) you'll also need to get a programming cable off of Ebay; any Yaesu VX6R/VX170 compatible cable should work. there are two types, one with the older RS232 serial port connector (DB9 type) and the other with a newer USB connector. i suggest that you get the latter type as the RS232 port is becoming less and less common on newer computers (especially on laptops). here is an EXAMPLE USB cable: cgi.ebay.com/USB-Programming-Cable-for-Yaesu-VX-6R-VX-7R-VX-170-VX6R_W0QQitemZ220259583364QQihZ012QQ note: i HAVE NOT used the above USB programming cable OR vendor; i link it merely as an example of what you should be looking for and the approximate cost. also note that some programming cables are generic in the sense that they don't have the *exact* connector needed for interfacing with the radio. this provides the vendor some flexibility since they are not making and stocking radio-specific cables. however, for you, the end user, a short adapter cable is needed to complete things. by way of an EXAMPLE, cgi.ebay.com/USB-Programming-Cable-for-Yaesu-VX-7R-VX-6R-VX-6E_W0QQitemZ360076336620QQihZ023QQ in the case above, the advertised cable does not directly interface to a VX6R etc -- one needs to get another cable, specifically Yaesu's CT-91. this info is noted in the auction text. the connector needed for the HX370S is a threaded, 4 conductor type, same as on the VX170, VX6R, and VX7R. you can see a closeup in this example auction: cgi.ebay.com/USB-program-cable-for-Yaesu-VX-6R-VX-6E-VX-7R-VX-7E-048_W0QQitemZ220264481835QQihZ012QQ  finally, the author of the popular FTBxxxx series of Yaesu programming software recommends, on this page, www.g4hfq.co.uk/links.html the following cable from Ebay vendor KAWAMALL: cgi.ebay.com/USB-Programming-cable-for-Yaesu-Vertex-VX-7R-VX-170-NEW_W0QQitemZ380051955508QQihZ025QQ again, i have no experience with this cable -- but the UK-based author of the Yaesu FTBxxxx series of programming SW definitely knows what he is doing. hope all that helps. |
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Posted: 8/11/2007 3:05:26 AM EDT
[Last Edit: ar-jedi]
[#34]
building a sound card interface: radio <--> PC (e.g. for RTTY and PSK31 audio)
---
excellent write-up above regarding interfacing the audio path. below, a simple DIY circuit for connecting many Icom and Yaesu radios with a PC's RS232 (serial) port for the purpose of using software (example 1, example 2) to program the radio. this circuit essentially duplicates the OPC478 cable offered (somewhat expensively, i might add) by Icom. this circuit is known to work with the Icom V8000, the Yaesu VX6R, and the Yaesu VX170. it should work with any Icom rig designed to use the OPC478 cable and most modern Yaesu mobiles/HTs(*). pics and schematic: losdos.dyndns.org:8080/public/ham/icom-opc478/ llosdos.dyndns.org:8080/public/ham/icom-opc478/IMG_1626_sm.jpg (*) some Yaesu rigs may require a 10K ohm pull-up resistor to 5V on the TX/RX lead. this biases the single wire net to Vcc, which these rigs evidently do not do internally. |
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Posted: 8/11/2007 3:09:43 AM EDT
[Last Edit: ar-jedi]
[#35]
expectations of privacy with amateur radio communications
it depends. for one, the intercepting party must be in the coverage area of at least one of the communicating parties -- in other words, to hear *at least* half of the conversation the intercepting party must receive enough signal for subsequent demodulation. the communicating parties can, in effect, hamper this by (a) minimizing the amount of power they use, (b) employing directional antennas, and (c) employing frequencies which minimize distant propagation. for an example of the last item, there is no way for the intercepting party to hear a 50W 440MHz signal at a range of more than about 100 miles -- the curvature of the earth simply doesn't allow it, and 440MHz (and above) is only minimally subject to atmospheric effects such as tropospheric ducting. for two, the intercepting party must have a radio which can be tuned to the frequency of interest, and a antenna and radio setup, which when combined, have sufficient sensitivity at the frequency of interest to pull the signal out of the noise floor. note that i have skipped right over actually finding the frequency of interest. this can be quite easy (for example, if the intercepting party directly observes the communicating parties using FRS radios), or it can be exceedingly difficult and require the use of an expensive, lab-grade spectrum analyzer and associated antenna(s). for three, the intercepting party must have a radio which uses compatible modulation to the two parties in conversation. by way of example -- if the two parties are communicating using SSB mode, and the intercepting party has only a handheld FM mode rig, the intercepting party is not going to be able to hear the conversation. the same situation occurs if the communicating parties are using a digital mode, like P25, and the intercepting party does not have equipment capable of P25.
amateur radio rules, in an effort to maintain a civil environment that all can enjoy, prohibit the transmission of codes or employing means to obscure the content of the communications.
in the USA, the Federal Communications Commission (FCC) regulates the entirety of the electromagnetic spectrum, including the frequencies assigned to amateur radio. since many amateur radio signals can and do propagate outside the boundaries of our borders, the FCC works with international bodies such as the ITU to help harmonize the use of frequencies worldwide. for example, *eventually* the foreign shortwave stations present at nighttime (USA time) on the 40m band *should* disappear as they are moved elsewhere.
that is simply not possible due foremost to the reasons i enumerated in the first part of my reply, and second because the amount of monitoring required would simply swamp any central body. hence, amateur radio is "self-policing" in the sense that ham operators are expected to govern their own operations, and to (i'm looking for the right term here) provide "guidance" to operators who choose not to abide by FCC rules and good amateur radio operating practices. the worst case is that the offending operator is reported to the FCC, which will then result in the FCC issuing a NAV (Notice of Apparent Violation) to the operator. this may be a result of, for example, maliciously interfering with the everyday operation of a repeater, or perhaps operating on a frequency which your license class does not grant you privileges on. operators receiving a NAV are given a short period to craft a response to the FCC, but if the FCC finds the response wanting, they will issue a NAL (Notice of Apparent Liability) which basically says that the operator is guilty of unlawful amateur radio operation and depending on the severity of the violation advises (a) don't do that again, or (b) pay the noted fine, or (c) surrender your amateur radio license, or (d) all of the above. e.g. www.fcc.gov/eb/FieldNotices/2003/DOC-237767A1.html
--
it depends. if i had, say, an unlimited US military size budget, i'd implement a spread spectrum, frequency hopping digital mode encrypted tactical squad/platoon radio system with a satellite uplink using a highly directional high gain dish antenna. from a land-based intercepting party's perspective, even a sensitive lab grade spectrum analyzer shows only a minor, non-descript increase in the ambient noise floor -- in other words, nothing seemingly interesting "pokes up". even if it were detectable, the intercepting party still needs (a) the correct digital demodulation type, (b) the correct decryption algorithm AND (c) the correct decryption key. none of these will be immediately obvious nor even recoverable by anyone but an extremely sophisticated, technically adept, and determined enemy. back to reality, using amateur radio gear for communications (e.g., during SHTF) is certainly less expensive. it does however mean that the level of sophistication, technical aptitude, and so on of a prospective intercepting party is significantly reduced. as an example, there is an entire aspect of amateur radio called "fox hunting" or "hidden transmitter hunting". a amateur radio club member plants a small, low power transmitter somewhere remote, and other members are challenged to discover it's location within a certain timespan. relatively inexpensive means are used to triangulate the location of the emissions. also, as you can see from the FCC example i cited above, this very same approach can be used for law enforcement activities as well. nevertheless, the very same radio procedures advised for military personnel in a combat zone can be used to defer detection of any type of radio communications -- frequent channel changes, keeping transmissions short, using OPSEC when communicating, need-to-know, etc etc etc. that said, if SHTF, i highly doubt that you will see bands of roaming Zombie "fox hunters" with sensitive receivers and small Yagi antennas looking for the source of your signal. note: if this does happen, i would suggest taping down the PTT key on one of your radios, placing it at the base of a tree, and then setting up a spotting scope and an AI AWSM in .338 Lapua about 500yds away. the buzzards will eat good. |
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Posted: 8/11/2007 3:18:26 AM EDT
[Last Edit: ar-jedi]
[#36]
ham radio and SHTF: discussion
---
tacked: www.ar15.com/forums/topic.html?b=10&f=22&t=612380
for HF, an Icom R75 receiver and an external antenna. for VHF/UHF, you might as well get a decent HT with an external AA pack. the FT60R comes to mind. then if you do need to xmit, you can, and it's portable. finally, by the time you are done you could have simply purchased an Icom 706MkIIG or a Yaesu FT857D/897D -- these are "shack in a box" rigs and will do everything you need to do. see www.ar15.com/forums/topic.html?b=10&f=22&t=614541 ---
here is a handy PDF denoting common HF frequencies used for emergency nets during times of national crisis, severe weather, and similar situations: www.ar15.com/forums/topic.html?b=10&f=22&t=612380 you will have to use an HF radio for regional/national/global news, and a VHF/UHF radio for local news. some radios these days, in fact the examples that i posted above, receive HF/VHF/UHF all in one box. you do need separate antennas for these bands.
there is no such thing new for under $200 unless you want a simple, inexpensive SW radio /or/ you want a VHF/UHF only radio for local communications. used, you may want to look at a HF rig such as the Icom IC735, Kenwood TS50, or Kenwood TS440/TS450. i would not bother getting a used HT as a new 2m HT is around $110, e.g. the Yaesu VX170.
10m-only is a waste of your time -- and at certain sunspot periods, like now, you won't hear much of anything. ---
all of the frequencies on the SHTF PDF frequency card are voice (SSB, AM, or FM).
all of the frequencies on the SHTF PDF frequency card are voice (SSB, AM, or FM).
all of the frequencies on the SHTF PDF frequency card are voice (SSB, AM, or FM).
there is no "one stop shopping" here. you will have to tune around the bands/frequencies listed on the SHTF PDF frequency card and gather intel. there is no "HF-based CNN" that you can simply dial into. if it were that easy, it would be just as easy for someone (even the government) to subvert it, right? summary: there is no one frequency which -- at all times of the day, all times of the sunspot cycle, and for varying distance from the SHTF epicenter -- will provide ALL of the information you are looking for. it ain't that easy. but it's not hard either. as a start, you may want to try the BBC or CBC SW broadcasts, since if our (USA) infrastructure is crippled our closest allies (England and Canada) may have useful information for you. you can also try listening to the time services out of Boulder/Ft Collins, as there are certain times per hour set up for dispersion of information of national importance. you can do the same with your local NOAA (VHF) station. and so on. finally, the control ops on the 14.300 marine maritime net are a great resource. if they don't know what is going on, no one knows what is going on. ALL THIS INFO, AND MORE, IS LISTED ON THE ABOVE LINKED SHTF PDF FREQUENCY CARD. if you have suggestions regarding other frequencies, or other modes, or anything else, please by all means make them known. my email address is on the card if you would rather do so in private. otherwise, print out that card, laminate it, and tape it to the top of your rig. ---
you need at worst two antennas. for HF: something like a long wire, OCF dipole, or G5RV. spending approximately $25 at Home Depot's electrical aisle would be a fantastic start. for VHF: a copper pipe Jpole or TV lead Jpole is about it; the former can be made for $20, the latter for $2. you could also splurge and get a dual band fiberglass antenna, like the $90 Diamond X50 -- and be good to go for the next 20 years. ---
you can do this with a $110 2m HT either simplex or via a repeater -- and also receive -) local NOAA "all-hazard" announcements including weather and amber alerts, -) local police and fire dispatch info if they are still on VHF high band, -) MURS radio transmissions, -) marine radio transmissions, -) and more. the 2m HT will operate on 6 x AA batteries. lithium primary batteries are good for 10 years. this is a good "closet radio" approach. keep a 12Vdc input power adapter as well, that way you can power the radio from your vehicle if/when you have to bug out. augment the 2m radio with a good shortwave radio and you are in business at low cost. |
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Posted: 8/11/2007 3:34:34 AM EDT
[Last Edit: ar-jedi]
[#37]
QRP operation (low power/portable)
for on-person carry, you have basically two options: (1) amateur VHF/UHF HT (handy-talkie). this type of radio looks and operates similar to what you see the typical police officer, firefighter, or EMT carrying around. small, lightweight, short antenna, with either an integral or a detachable battery pack, an HT can be hung from your belt, clipped to your molle/etc, or stowed in your backpack. HT's are used to talk in one of three ways: HT to HT (called simplex operation), HT to fixed station/base (also called simplex), or HT to repeater. while the first two scenarios are quite range-limited due to the low power output of the HT (typ 5W) and the small antenna (typ ~4" to 15"), the repeater situation is altogether a different one. utilizing a repeater, an HT can be used to communicate over an area of hundreds of square miles. i explain repeater operation in detail about 3 or 4 posts down in the Ham Radio 101 thread which is permanently tacked to the top of this forum. just to close up on VHF/UHF, depending on where you live there may be from 0 to 10 repeaters reachable using an HT. if you are way out in the sticks, it will likely be 0. if you are near a relatively populated area, it will be more like 5. examples of VHF/UHF HT's are the Yaesu VX170 (2 meter only=VHF) and the dual band Yaesu VX6R (2m and 70cm=VHF/UHF). this class of radios generally cost around US$130->US$250, depending on features. (2) low power amateur HF radio (also called a QRP radio). QRP is a "Q-signal" meaning "reduce your power". in the amateur community, the term "QRP radio" generally describes an HF rig which outputs around 5W, although some models produce up to 10W. a QRP radio also has features which minimize power consumption while receiving. for example, there will be settings to turn off all of the display and key backlights, and so on. and, a QRP rig will work on lower DC input voltages than typical HF radios, which in turn facilitates operation from different types of battery packs. why use a QRP radio? well, for remote operation (either on foot or at a campsite), the amount of available battery power will limit operating time and transmit power. hence, a QRP radio maximizes your overall operating time. with a QRP HF radio, you can talk either about 5000 feet, or about 5000 miles -- depending on band conditions, the quality of your antenna, soil resistivity, quality of your receiver, and your ear. QRP is a real "art form" in amateur radio; you generally have to know what you are doing to make DX (distance) contacts, and this requires practice, dexterity in antenna hanging, familiarity with the quirks of the ionosphere, complete knowledge of advanced features of your radio, and a keen ear for tuning. now the tough part. the primary issue with operating HF while portable is the antenna. HF requires long antennas for efficient transmitting and receiving; a short antenna hurts on both counts. hence, the antenna is the critical factor for remote operation. you can play this two ways: (a) operate while walking with a vertical antenna sticking up out of your pack, or (b) operate while at camp using an antenna you assemble from your pack. option (a) is employed by many folks; you can see some nice pics here (click on the Meet the Moderators jpegs at the bottom): www.hfpack.com/ note that Europeans, especially those in the UK, are especially active in man-portable QRP operation. they dig it. option (b) is employed by many folks as well. you simply bring along a radio, a battery, and a portable antenna, and set it all up on a picnic bench at camp. the antenna can be a roll-up type (google "yo-yo-tenna") or a pre-fab dipole type which assembles like a tent pole (google "buddipole"). typical all-mode radios for QRP operation include the Icom 703+, and the Yaesu FT817ND. the former is popular with the picnic table crowd, and the latter is extremely popular with the manpack crowd. note that these are multi-purpose, all-band, all-mode radios that also double as shortwave (SW) receivers. there are also available some very simple, very power-efficent HF QRP radios that operate CW (morse code) on a single band. these types define the true essence of QRP operation: simple, low power, task-specific radio. any way you do QRP, you'll need an external antenna of some type, a microphone (for voice) or a key (for CW), and ideally as much battery capacity as you can carry. more QRP info/links here: en.wikipedia.org/wiki/QRP_operation also see home.frognet.net/~mcfadden/wd8rif/seorat.htm www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=11136 Icom 703+ in an example pack: (link)  final note: almost every high power (100W) HF rig can be dialed back to output only 5W, or thereabouts. hence, you can "run QRP" with a radio such as the Icom 718. however, current consumption on receive with a non-QRP rig will be much higher than a true, designed-for-QRP radio. this will impact battery life significantly. an example comparison: Icom 706MkIIG HF radio --> ~ 1.5A on receive. Icom 703+ QRP HF radio --> ~ 0.3A on receive. --
ah yes, the perennial ham radio question.
this is called a "QRP" (=low power, typ 5W) radio. like the Icom 703+, it has a defined purpose in mind: man- or field-portable radio.
correct. the 5W is where the trouble starts...
on VHF/UHF, the range is going to be the same as a generic 5W output dual band HT (FT60R/VX6R), assuming you use similar antennas. HF is a different story altogether. on a really good day, 5 watts and a decent antenna will get you 5000 miles. on a bad day it will get you about 5000 feet. on all of the days in the middle, it will be hit or miss. with 5w output, you will likely be able to hear many more stations than you can talk back to. these days, the noise floor of good amateur receivers is below the noise level of the atmosphere. with a good aerial, you'll definitely hear DX stations all over the world. with 5W, it will be tough to get back to them. even 80m, which is a regional band, will present difficulties talking into the next state. so now you are asking, "ar-jedi, you have not painted a very positive picture here. clearly Yaesu had some purpose in mind for the FT817, and hell -- from what i've read -- worldwide Yeasu has sold something on the order of a hundred thousand of these radios, plus over on Eham people seem to love them. so, what's the deal?" the deal is that HF QRP radios fit a defined purpose -- low power portable operation, and you need to understand the limitations of such. you need a good HF antenna -- an efficient antenna is a must. morever, QRP begs for using CW (morse code), and more recently the digital mode PSK31. these are modes uniquely suited to low power operation. all this good stuff (antenna + CW) may add up to squat if the ionosphere is just a little uncooperative though. there are no guarantees with HF operation, ever, no matter how much power you run. with just 5w, there is that much less leeway. the upside is that QRP radios sip electrical power at a rate that embarrasses most all QRO (typ. 100W or higher) rigs. and, QRP radios operate down to far lower voltages than typical QRO rigs. hence they are far lighter as a system, since you don't have to carry such a big battery pack.
this is not optional -- you will HAVE to. google Buddipole, Buddistick, YoYoTenna, and so on. the choice of VHF/UHF antenna is arbitrary. you can use a rubber ducky or something with more gain.
no. i've looked into this extensively for my Icom 703+. the answer is no. stop looking, it is a waste of money to try to do it. folks are going to point you to the Tokyo Hi-Power FT817 companion amp, and you'll stop in your tracks when you see the price tag. put the idea of an external amp out of your mind. you can buy a used FT857 for a tiny bit more than what a used HL-100BDX will cost you. and the import situation is awkward as well.
yes, and no. sucky answer, i know. most experienced hams will steer new hams away from HF QRP radios. their rationale is that there is little margin for error with QRP. if your antenna is poor, if your SWR is high, if your feedline is lossy, and so on, you will have difficulty. if the sunspots are not out, you are going nowhere with 5w. put a 5w bulb in a nightlight, and turn it and only it on at night. you can hardly see the other end of the room. a 100w bulb changes things dramatically, doesn't it? the other argument is that the FT817 makes a poor HT; you can buy a FT60R/VX6R, which is a "proper" HT, and it gets the NOAA weather stations as well (~162.5MHz, where [astonishingly] the Yeasu FT817 will not receive). another point is that more and more HT's are truly waterproof, which makes them more field-portable than the FT817. that said... if you are the patient, thinking type, and you realize that you are not going to QSO with Germany every day on 20m with 5w, and maybe not even once a month -- and you desire a lightweight, power efficient radio and you have the funds and/or the time to buy/build various portable antennas, then a QRP radio might be for you. if you plan on doing a lot more listening than transmitting, a QRP radio might be for you as well. you can get the BBC or listen to statewide rag chews on 80m very easily on the FT817, and it sips power while you are doing it.
get a mobile radio, like the FT857, and a power supply (such as the Samlex 1223). instant fixed station.
yes, you do... keep reading.
talking to folks in "other states" implies needing HF, unless you have a very widespread linked VHF/UHF repeater system nearby. so you need HF. that means you need a big antenna (figure $20-100 for one, depending on what you do) and a tuner (unless it's built into the radio, figure on spending $70-175 for a good one, for example from LDG). ---
see www.ar15.com/forums/topic.html?b=10&f=22&t=593963 the Icom 703+ QRP radio that i use has an integral autotuner. it is actually quite capable, and will match beyond the 3:1 that is advertised on the spec sheet. however, it does have it's limitations -- it will not match an end fed random wire (~3000 ohm feedpoint), for example. so you need a "reasonably resonant" antenna to drive. i've been using two antennas -- first is the commercial Yo-Yo-Tenna Deluxe (link). this a a dipole type which you extend as needed to the band of interest. next, i use a homebuilt UnUn to drive a end-fed sloper antenna. you'll need to buy/build such a device and then you'll need 2 pcs of 28AWG wire about 50 feet long. i throw one wire over a tree branch (i cleverly have an old 1/2" copper elbow soldered on the end for weight) and then you extend the other wire (the counterpoise) along the ground underneath the former wire. here is the design i copied: (link). also see (link).
here is the problem: with a 100W output (QRO) radio everything gets bigger: the tuner, the battery, etc. -- all of this contributes to a bigger and heavier box. non-QRP radios are not really designed for (1) really low current consumption on receive, nor (2) operation from voltages lower than about 11.7Vdc (that's 13.8Vdc - 15%). hence, you don't get nearly as much mileage out of your battery capacity with a non-QRP rig. of course, the limitation is that you get fewer watts out the RF connector... if you decide to go with a 100W radio might i suggest looking at the Yaesu FT450AT? it's relatively small, has an integral autotuner, has IF DSP, and right now it's priced very attractively ((link). this radio has gotten it's fair share of good reviews over on Eham (link). since you have dual band VHF/UHF on the FT8000 already, you just need an HF rig. the internal autotuner on the FT450 will save you a lot of space, and save you the space needed to link the rig with the tuner via coax. in the end i decided that the difference between 10W and 100W was not worth the added weight and reduced operating time. in fact, in my view one would mostly be *listening* during SHTF/TEOTWAWKI, not transmitting. at ~300mA, QRP radios sip power on receive. yes, you'll need to get the wire up up higher and such to get the same reach on transmit as a 100W radio. but i don't plan to need to bust pileups during SHTF. |
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Posted: 8/14/2007 12:20:45 AM EDT
[Last Edit: ar-jedi]
[#38]
HF antennas, a work in progress a dipole antenna, graphic courtesy of Scottman:  a fan dipole, graphic courtesy of Scottman:  ---
+1M on the G5RV. here is the one to get: ebay link reviews and more info: www.eham.net/reviews/detail/2202 i have this antenna strung up between two trees, only about 20' high, and it works great. it is extraordinarily constructed, top quality heavy duty parts everywhere right down to the silver/teflon PL259 connector. --
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Posted: 8/14/2007 12:22:11 AM EDT
[Last Edit: ar-jedi]
[#39]
The UPS guy delivered your first HF radio –– Now what? PHASE 1: (0) Erect an antenna of some sort. It could be a commercial product or a simple wire dipole. Longer, better. Higher, better. (1) Forget about transmitting –– for at least 7 days. Learn to receive first! This isn't VHF/UHF FM –– most SSB signals are not just going to jump out at you. At times, QSO's may be going on nearly on top of each other, and how you tune and use your radio's various features will determine how well you can hear. Moreover, there is no "squelch" function in SSB-land; you can't just set the radio to scan for active frequencies. (2) Tune for beacons located in the USA; for frequencies see mega list of beacons. (3) Tune for WWV (USA) / CHU (Canda) time stations: 2.5MHz, 5Mhz, 10MHz, 15MHz, 20Mhz / 3.330MHz, 7.335Mhz, 14.670MHz. (All are AM mode. You will hear a once-per-second click, and then a voice announcing what the time in UTC will be "at the tone"). (4) Tune for active QSO's in the phone and CW areas of 80m, 40m, and 20m bands. These *should* be fairly easy to find. Don't forget to switch modes (CW, LSB, USB) as you tune around the bands. Learn to recognize the "Donald Duck" quack sound of being a little off of a strong SSB signal, and which way to tune based on the sound. (5) Copy down some call signs from the QSO's you've heard, and look up those calls in the upper left hand corner here. Then click the "Details" link, which will give you a page similar to this. (6) Note the locations of the beacons and stations you are hearing. This information gives you a good idea which way your optimum paths are and what the propagation situation is currently like. Compare this data with beacons and stations heard at different times of the day. (7) Look up the "DX windows" for the 160m, 80m, and 40m bands. Listen for "CQ DX" calls from US amateurs. See if you can hear both ends of the ensuing QSO's. (BTW, if you are a US station, do not answer CQ DX calls from a US station! –– Instant LID status will result). (8) Read your manual and understand the benefits and side-effects of the receive mode features of your radio –– for example, DSP noise reduction and so forth. Employ these features to help resolve weak stations and/or cut down on hiss and band noise (QRM). a few things you will note: –– the top (phone area) of 40m is shared with foreign AM broadcast stations. you will hear these at night, a lot. –– google for an online list of shortwave (SW) radio stations, like the BBC World News or Radio Free Europe. their prime transmitting times don't always coincide with your chosen listening times, but you'll find some interesting stuff in the SW bands. –– from a DX standpoint, 10m through 15m is pretty poor right now due to where we are in the sunspot cycle. these bands will pick up over the next few years. PHASE 2: Listen... tune... and listen more. And listen to some well known/well run HF nets: www.14300.net/ www.smeter.net/stations/hf-amateur-radio-nets.php www.smeter.net/stations/hf-stations.php www.ecars7255.com/ More time stations: www.smeter.net/stations/hf-time-frequency.php –– Originally Posted By R-32:
Originally Posted By Jamess67:
I have the 857d,,,, Now I just have to figure out how to use it. switch over to 40M band, start spinning the funny looking knob... keep in mind that the 40m band is currently shared with international shortwave stations; at nighttime (in the USA) you will get tons of interference on 40m. if you want to listen to Croatian music or Radio Netherlands, simply wait until it's dark, switch your rig to AM, and tune around the 40m band. my advice for breaking a new HF radio/user is to try 20m/40m during the day –– but at night 80m is likely a more usable band unless you can find a quiet hole on 40m to sit in. at least that's the way it is here on the east coast. –– en.wikipedia.org/wiki/20_meters The 20 meter amateur radio band is a portion of the shortwave radio spectrum, comprising frequencies stretching from 14.000 MHz to 14.350 MHz.[1] The 20 meter band was first made available to amateurs in the United States by the Third National Radio Conference[2] on October 10th, 1924.
The 20 meter band is widely considered among the best for DXing, and is one of the most popular (and crowded) during contests.[3] Several factors contribute to this, including the band's large size, the relatively small size of antennas tuned to it (especially as compared to antennas for 40 or 80 meters) and its good potential for daytime DX operation even in unfavorable propagation conditions. en.wikipedia.org/wiki/40_meters The 40 meters or 7 MHz band is a core amateur radio frequency band, spanning 7000 to 7300 kilohertz, allocated to radio amateurs in all countries worldwide. The 40 meter band was made available to amateurs in the United States by the Third National Radio Conference on October 10th, 1924. 40 meters is considered the most reliable all-season DX band, most useful for inter-continental communication at night. It is extremely useful for short to medium distance contacts from local contacts out to a range of 500–1500 km, depending on conditions, during the day. In higher latitudes, daytime inter-continental communication is also possible in winter, for example a good path often opens between Japan and northern Europe in the hours leading up to European midday from late November until late January, with a long path opening to the west coast of the United States and Canada after midday.
For many years the portion of the band from 7100-7300 kilohertz has been allocated to short wave broadcasters outside the Americas and not available to radio amateurs outside ITU Region 2. At the World Radio Conference WRC-03 in 2003 it was agreed that the broadcast stations would move out of the section 7100-7200 kiloherz on 29 March 2009 and that portion would become a worldwide exclusive amateur allocation afterwards. Discussions on releasing the remaining 100 kHz of the band to amateurs at a later date will continue in future conferences. Several European countries have now allowed amateur communication in the 7100-7200 kilohertz section on a shared non-interference basis as an interim measure. Due to the 24 hour nature of the band, the wide variety of ranges that can be spanned with it, and its shared nature, it tends to be extremely crowded, and interference from other amateurs and broadcasters can be a serious limiting factor. In addition, amateurs in east and south-east Asia have suffered severe interference from illegal users in recent years. en.wikipedia.org/wiki/80_meters The 80 meter or 3.5 MHz band is a core amateur radio frequency band, allocated frequencies from 3.5 to 4.0 MHz in IARU Region 2, and generally 3.5 to 3.8 or 3.9 MHz in Regions 1 and 3 respectively. The portion of the band used for voice communications is sometimes referred to as "75 meters". The 80 meter band was made available to amateurs in the United States by the Third National Radio Conference on October 10th, 1924. 80 meters is the most popular band for regional communications networks through the late afternoon and night time hours. It is usually reliable for short to medium distance contacts, with average distances ranging from local contacts within 200 miles/300 km out to a distance of 1,000 miles/1,600 km or more, depending on atmospheric and ionospheric conditions.
–– Originally Posted By jagchaser:
I stopped in a radio store yesterday and bought a icom ic-706mkIIG and a 80/40/20/15/10 meter parallel dipole antenna. Anybody on now that I could try to listen in on? tons of people! you just have to find them... here is a reference card that will be handy: http://www.ar15.com/forums/topic.html?b=10&f=22&t=612380 remember though, that you need to have AT LEAST two things – that is not a problem whatsoever. let's play a bit... first some easy stuff... note that in no case should you transmit below! you can simply disconnect the microphone for now. your 706 receives VHF FM. so, connect your big HF antenna (temporarily!) to the VHF RF connector. tune around 162.55MHz FM. hear NOAA announcing the weather on several nearby frequencies? very good. you'll note that the exact frequencies for the NOAA stations are documented on the card above. there are seven frequencies –– one will be strongest in your area. with the big antenna still connected to the VHF connector, tune around 121MHz but switch the mode to AM. rolling around there, you *should* be able to pick up some aircraft transmissions, although this may be a no-go if you are far from a metro area or well off the air routes. keeping the antenna on the VHF connector, tune around 144-148MHz FM –– this is the 2m ham band. a little bit of research in the Ham 101 thread (page 1, about halfway down) will point you towards an online reference for finding local repeaters. you should be able to hear conversations on the repeaters, or perhaps just the repeater key up every 10 minutes and ID itself (may be in voice or morse code). now switch the antenna back over to the HF input. tune to 10MHz AM. you may be able to hear the tick-tick-ticking of the WWV time station coming from Ft Collins Colorado. after the 50th second of every minute, an automated voice will announce, "at the tone, the time will be XX:YY". now tune to 5MHz AM , and then to 20MHz AM. all of these signals come from the same place, but how well you can hear them is a function of the ionosphere and your antenna system. again, these frequencies are illustrated on the card linked above. since it's dark now, your best bet for hearing ham QSO's (clever name for conversations) is to tune around the 75/80m band –– 3.500 to 4.000MHz. near the bottom of the band you will have to switch to CW mode, and you'll hear folks sending morse code. north of 3.600MHz, switch to LSB and slowly tune for voice amateur radio traffic. tuning in HF-land requires a bit of acquired ear –– don't get frustrated at first. during the day, 40m band traffic will pick up as well –– and without the interference caused by the shared use of the top of the 40m band by international SW broadcasters. 40m is CW at the bottom (below 7125), LSB at the top. on any day after about noon eastern, there is almost no way you will not be able to hear traffic on 14.300MHz USB (20m ham band). the marine maritime net has been running there for 30+ years. net control stations will announce themselves and solicit check-ins. you may not be able to hear both sides of these conversations –– this is always an issue with long distance radio communications. finally, a note about your radio controls. the RF gain dial and preamp button need the most consideration. initially, leave the preamp off and put the RF gain control at about the 12 o'clock position. when you tune in a station, try to back the RF gain down until the background noise is minimized but you can still hear everyone. using the preamp is sometimes a necessary evil for pulling in weak stations, but it does have the side effect of raising the noise floor somewhat as well. soon afterward you'll learn that a modest amount of DSP NR (set it to 2, 3, or 4 initally) will make tuning and listening more pleasant by cutting out a lot of background noise. –– Originally Posted By jagchaser:
Maybe this is what has lost me. There are 2 ports for the antenna and they just say ant 1 and ant2. I dont see anywhere to hook it up to VHF. look on the side of the 706mkII chassis adjacent to the connectors. click here: http://losdos.dyndns.org:8080/public/ham/icom-706mkIIg/pics/DSCN3863.JPG the top one says "ANT 1 HF/50" <–– that is for HF and 6meters the bottom one says "ANT 2 144/430" <–– that is for VHF (2m) and UHF (70cm). –– Originally Posted By jagchaser:
I can get a few stations with morse code in the 3600-4000 LSB but I am not hearing any conversations yet. I wonder if I need a tuner for this thing? a tuner is not required to receive. Originally Posted By jagchaser:
There I found something at 3.720 I cant really make out what they are talking about but there are 2 guys discussing something. if the audio sounds distorted it is because you are off frequency a bit. tune up or down a bit and see if it improves either way. tomorrow try out 20m and 40m, the latter you should get some activity on and there won't be the interfering noise from europe. listening to WWV on several frequencies (2.5, 5, 10, 20) will aid in determining propagation in that direction. also see the canadian time station equivalents (note that one of the CHU frequencies has changed effective 01 JAN 2009, and the SHTF card does not reflect that yet). |
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Posted: 8/14/2007 12:22:51 AM EDT
[Last Edit: ar-jedi]
[#40]
using an external autotuner
i don't have an 857 or Z100, but... generally when you press the Tune button on a modern rig OR do the same via an external tuner which is umbilical'd to a modern rig, the radio switches to CW mode, injects a 2KHz carrier to the audio path, and turns on the transmitter at about 5W. the directional coupler at the RF TX egress point measures the reflected power, and then the radio (if equipped w/ an internal tuner) or external tuner (like yours) starts a binary search of L and C values to find the correct match for the load. a few seconds later, the tuner will have found a match and transmitting will be halted. the radio mode will be auto-returned to its previous setting (e.g. USB), so no further manual action should need to be taken by you. at this point you are ready to go on with transmitting. note that most tuners (internal and external) have features to remember prior search results. that is, they store the transmit frequency and the discovered L/C combination in a lookup table. later, if you re-initiate a tune near that frequency, the radio uses the remembered L/C values as a starting point. this effectively reduces the time to tune.
the radio, upon getting a "tune now" signal from the tuner, should temporarily switch to CW as noted above. when tuning is complete, the tuner will negate the "tune now" signal and the radio will swap back to your original settings. btw, you can't tune up in SSB without some audio input -- keep reading...
completely normal. in SSB mode the radio transmits essentially no RF power when there is no audio input. you'll note that if you whistle or speak when TX'ing, the power meter will (should) indicate higher RF output. this is the basis of SSB (suppressed carrier) modulation: no audio input, no RF output. contrast with FM, where there is ALWAYS 100% RF output regardless of audio input. ps: initially, you will have to play with your microphone gain and speech compressor settings a little bit to get your audio (as received at the other end) "peaked". this is dependent on your voice characteristics, how loud you speak into the mic, how far it is from your mouth, etc -- your best bet is to find a local ham, and talk to him on SSB to give you some feedback on your voice quality. beware if you crank up the mic gain and/or speech compressor settings too much, it will sound like crap. first, use the default settings from your manual, and work from there in gradual steps. --- |
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Posted: 1/22/2008 9:35:37 AM EDT
[Last Edit: ar-jedi]
[#41]
HF baluns explained
for what frequency? you can make a balun for HF quite easily. you can't make a balun for UHF easily. there is a great ARRL text on this subject, "Understanding, Building and Using Baluns and Ununs" www.arrl.org/catalog/images/8982.jpg you can order it from the ARRL website, about 90% of the way down the page here. ps: to everyone wondering what a balun is: en.wikipedia.org/wiki/Balun
BALUN is a concatenation of "BALANCED-UNBALANCED" and generally refers to a device which takes a balanced signal and converts it to an unbalanced signal, or vice versa. now then, what's that mean? in a balanced transmission line, there are two conductors which carry equal but opposite signals. (you could also say that the second signal is phase-shifted 180deg from the first). there is no "ground" per se in this mode. 300ohm TV lead, and 450ohm ladder line are examples of cables that carry balanced signals. (aside to EE's: balanced can be looked at as differential signaling). in an unbalanced transmission line, there is one conductor which carries the signal and the other conductor is a reference, generally "ground". (aside to EE's: unbalanced can be looked at as single ended signaling). one method or the other is not a better way to carry RF, in other words both unbalanced and balanced transmission lines can work equally well. so why do we care? for two reasons: 1) the output of a amateur radio transceiver is typically unbalanced. however, a great many antenna designs (for example, a true dipole) really want to be driven by a balanced source. enter the BALUN, which uses a transformer or a matching section of some sort to convert the signal from one type to the other. 2) the use of ladder line is cumbersome due to the fact that nearby any metal changes the characteristic impedance. for example, if you tie wrap ladder line to a tall tower, you may discover the impedance of that section has wandered way off from what you'd expect. coaxial cable does not suffer from this problem, as the signal-carrying conductor is completely and equally surrounded by the braid and/or foil shield which is the reference. so we are kinda stuck here -- it's more practical to carry RF signals on coaxial cable, but lots of antenna types want a balanced signal as input. and that's why BALUNs exist, to meld the two together.
not quite. the ideal reference antenna is a dipole. let's use 2M FM as an example -- there is a 1/4wavelength radiator up, and a 1/4wavelength radiator down. the overall height therefore is 1/2wavelength, or about 1 meter. the "counterpoise" is the element on the bottom. is is a necessary, essential part of the dipole and can not be ignored nor done away with. it does not reflect anything either; it is a radiating/receiving element, just as the top part of the dipole is. however, it is possible to substitute a real metallic ground plane, or perhaps a "virtual ground plane" using short downward sloping elements. this is typically referred to as a 1/4wavelength ground plane antenna. the lower half of the ideal dipole is mimicked by the ground plane. (incidentally from above it should now be apparent to you that a dipole antenna really wants a balanced signal fed to it, that is one with one signal 180degrees out of phase from the other. if a dipole is fed with coax cable, RF currents can be found on the shield of the cable and this will distort the raditation pattern.) n.b. some antennas have non-driven elements parallel to the radiating element; the elements behind the driven element are called reflectors. a three element yagi, for example, consists of a driven element (it's really just a regular dipole antenna), a reflector behind it, and a director in front of it. compared to the dipole on the middle, the reflector is marginally longer, and the director is marginally shorter. |
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Posted: 1/22/2008 9:35:49 AM EDT
[Last Edit: ar-jedi]
[#42]
programming cables and SW for VHF/UHF radios
i have a VX6R and an FT8800. regarding programming... you only need one cable, and an adapter (which you can make yourself if handy, see the following thread): archive.ar15.com/forums/topic.html?b=10&f=22&t=610833 you need two pieces of software: www.kc8unj.com/vx6.html <-- donation-ware www.g4hfq.co.uk/ftb8800.htm <-- US$18.50 the latter can import from the former. so, manually enter all of your frequencies into VX6R Commander; program your VX6R; import the data file into FTB8800; program your FT8800 -- effectively, the two radios are now cloned, and all of your channel numbers/names/etc will be the same. --
as noted above, get FTB8800.
yes.
the electrical layer protocol for the VX6R and FT8800 are exactly the same. all you need to do to use a VX6R cable with the FT8800 is make a short (passive) "converter" cable to adopt the 1/8" plug to a DIN connector. the easiest way to go is to find an old PS2-style mouse or keyboard, and snip the DIN connector off, leaving about a 6" tail on it. at radio shack or equivalent, obtain a 1/8" stereo (3 conductor) jack (not plug). the jack can then be soldered onto the end of the stub you just cut off, and you are in business. insert the VX6R programming plug into the jack, and insert the DIN connector into the back of the radio. if you want to go this way let me know and i will provide the correct connections (a whopping 2) for the adapter cable. i made a similar adapter myself to use with my FT8800. you don't need 90% of what you see in the pics below -- just a 6" end piece of old keyboard/mouse cable, a 1/8" jack, and a hot soldering iron. losdos.dyndns.org:8080/public/ham/yaesu-ft8800r/pics/DSCN3170_sm.jpg losdos.dyndns.org:8080/public/ham/yaesu-ft8800r/pics/DSCN3172_sm.jpg --
i rec'd an IM requesting "how"... on the DIN connector (and therefore the back of the FT8800), PIN 2 is ground. PIN 3 is data. here is the view AS SEEN ON THE RADIO JACK (the female side = sockets):  here is the view AS SEEN ON THE CABLE END (the male side = pins):  also see www.burtonsys.com/PS2_keyboard_and_mouse_mini-DIN-6_connector_pinouts.html and losdos.dyndns.org:8080/public/ham/yaesu-ft8800r/pics/DSCN3172_sm.jpg to program your VX6R, you have either a CT91 "Y" adapter, or some kind of special cable that has a 4 conductor plug on the end. i'll assume first you have a CT91...   on the VX6R's "stereo" 3.5mm connector, there are three connections: tip, ring, and ground. the tip, well, is self-explanatory. the ring is set just behind the tip and insulated from it. the ground is the rest of the metallic part of the connector, and is sometimes called the sleeve. the ground (sleeve) is ground. the ring is data  hence, configure your NEW FT8800 adapter cable to connect DIN PIN 2 to ground (sleeve), and DIN PIN 3 to ring. this allows use of the VX5/6/7's CT91 "Y" adapter with the FT8800. if your cable has that special (stupid?) 4 conductor screw-in plug on it, the same connection scheme is used. in this case, there are two rings, one closer to the tip and another behind it. the one closer to the tip is the data. the ground (sleeve) is the same.   n.b. there is a ton of info on the cables/pinouts/etc at www.kc8unj.com/ click on " Interface Cables " in the left panel. --
the problem sounds suspiciously like you don't have the ground wire connected up correctly. the usual symptom for this is that the reads are corrupt. check your cable's ground wiring. did you buzz out your DIN connector? or said another way, how did you determine what wire goes where in the DIN connector that you cut off the mouse or keyboard? --
--
i take paypal.  the above just-get-the-right-connector approach works for ANY Yaesu radio (base, mobile, or HT) and also works for ANY CI-V equipped Icom radio (base, mobile, or HT). i use the same level converter assembly (shown above) with the following radios:
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Posted: 1/22/2008 9:35:59 AM EDT
[Last Edit: ar-jedi]
[#43]
example HF station, KISS-style (KISS = keep it simple, stupid!) new HF/ham folks, shown below is an EXAMPLE of a HF/VHF/UHF "all mode" fixed station. this minimalist station consists of a radio, an automatic antenna tuner, and a power supply. not shown are the two (2) antennas (one for HF, another for VHF/UHF) which are located outside the house at the end of the two coax cables shown disconnected. the radio (box in the middle with the most dials and big display) is an Icom IC706MkIIg, which is a so-called "shack-in-a-box" rig. it covers all bands from 160m up through 70cm, all modes across AM/FM/SSB/CW, and of course has a wideband general coverage receiver as well (meaning, you can listen to shortwave stations, the local police, etc). this radio, like many of it's direct competitors, outputs 100W of RF on the HF bands, and about half that on the VHF/UHF bands. the 706MkIIg is small enough to be used mobile, but many folks use them for fixed station use. the control faceplate is removable and can be remotely mounted from the larger RF unit. the attached microphone allows FM and SSB (phone) voice modes; a key or paddle would be required in order to send CW (morse code). the automatic antenna tuner (box marked "LDG AT-7000" with no controls) is needed to help match the HF antenna's characteristic impedance at a given frequency to the radio's output impedance (nominally 50ohms). operation without the tuner is certainly possible, but it places more stringent considerations on the antenna employed and in most cases will limit the bands which can be used. this particular auto-tuner is controlled via a pushbutton switch on the radio itself; depressing the switch momentarily initiates a tuning cycle, during which the tuner spends a few seconds autonomously searching for a good match between the radio and antenna. when the tuning cycle is complete, the radio is ready to go for communications. (note: other types of antenna tuners are available; for example, some require observing a meter while manually manipulating of a set of dials to match the antenna to the radio at the desired frequency). the power supply (box marked "SEC 1223" with the power switch) simply takes 120Vac from the wall socket and converts it to DC at approximately 13.8Vdc. most all amateur radios are designed to accept 12Vdc nominal. the radio it powers requires about 20A DC input for full RF output; the power supply shown has an output rating of 23A, so there is approximately 10% headroom here. with a fixed station setup such as this, one can communicate locally using VHF/UHF, and nationally/globally using HF. i can't stress enough though that 7/8ths of the performance of this type of station is due to the antennas outside, and not the equipment on the desktop. the most expensive radio in the world is a paperweight without a good antenna system. note that similar setups can be constructed using Yaesu and Kenwood equipment. directly comparable to the Icom 706MkIIg shown is the Yaesu FT857D. in the case of some radios -- the Yaesu FT450, Kenwood TS2000, and Icom 746Pro come to mind -- the antenna tuner is incorporated into the radio itself. this saves some desk space, and in some cases may simplify operation to some extent. as you can see from one of the pictures, the HF output of the radio (upper RF connector) is umbilical'd to the antenna tuner via a short coax jumper, and the antenna itself would be connected to the tuner. in other words, the antenna tuner sits between the radio and the HF antenna. the VHF/UHF output of the radio (lower RF connector) would be directly attached to the outside VHF/UHF dual band antenna. there is a short, lightweight interconnecting cable between the radio and the antenna tuner that carries control signals. and finally, there is a heavy gauge cable that carries 13.8Vdc at high current from the power supply to the radio. while shown as a fixed station, this setup can be easily transported in a hard sided case. an enclosure with internal dimensions of approximately 8"H x 8"W x 12"D would be needed. the total weight of the three components shown in the pictures is approximately 10 pounds.         |
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Posted: 7/20/2008 12:16:56 PM EDT
[Last Edit: ar-jedi]
[#44]
What is an Azimuthal Map and why do I need one? Originally Posted By A_Free_Man:
We all know that conventional flat maps give a distorted view of theworld, especially as you get further north. It is difficult tounderstand why a flight from NY to London would pass over Greenland, ora flight from the US to Tokyo going over Alaska. The "Great Circle" andall that. An "Azmuthal Map" places YOU, yes YOU at the center of your ownlittle universe where you properly belong. It redraws the map of theworld with your location at the center. You can more easily figure outthe proper heading for signals from you to whereever, how to aim yourantenna, and other nifty information. AR-Jedi can jump in here and tellus more about propagation, and how all this fits together so you canget that QSL card from that some little country most of us have neverheard of. So, where do I get one of these nifty maps? Here's one I found, afreeware, with a short Google search. It's called AZMap and you canread about it here: http://aa6z.tripod.com/id2.html Once you have it installed you'll have to find it in C:>ProgramFiles. It won't be listed in the menu. It will be in a folder calledAZMap. To get the program to open you'll have to double click on thefile AZMAP2.exe. I dragged it over to the start menu and made ashortcut there to add it to the menu. OK, start it up with a double click. Well, first thing you noticeis you are not the center of this universe. We can fix that. Go to QRZ.com and enter your call sign. When yout get to your page,click on Detailed Info. Now, write down your coordinates, Latitude andLongitude. Now back to AZMap... Look in that AZMap folder. You will find twofiles, Atlas1.txt and Locations.txt. Open them. These are simple textfiles, and you can add (put it in alphabetical order) your town, callsign prefix, and coordinates. If the first numbers (Latitude) ispositive, it is North, so use an N in the next column, then theLatitude rounded off to two decimal places. If the second number(Longitude) was +, you will enter E for east, and if negative, as itwill be for the US, enter w for West. Add a zero in front to makeLongitude a three digit number if necessary. Line up your columns withthe ones above and below. You can paste the same line you typed inAtlas1.txt into Locations.txt. You can also add friends towns andlocation info. Close and save. Now, go to File and open AZMap. Click File, Create New Map, andclick "Select from a List". Chose your location from the list and clickOK. You should now see a neat map with your location dead center. Seethe darker area? That is where the sun don't shine... no, not thatplace... places where it is after sundown. If you don't see it, in theMap Display Control Panel check "Show Terminator". This would be goodto know if you want to do try some "gray line" propagation. Over on the right in the Map Display Control Panel you can selectfrom a list. If you had entered your friends' locations in those filesI told you about earlier, you'd find them there. Or you can enter anyother Latitude and Longitude. Note the time display, click the Set TimeTo Now button, and time will be in UTC time, Zulu time, Greenwich MeanTime, or whatever is the flavor of the day. Over in the Map DisplayControl Panel check Auto-Update Time. Every so often you will see themap flash. That is the terminator line (sunrise, sunset) being redrawn. And when you enter your friends location in the Map Display ControlPanel you get a nice red line drawn from your place to theirs, and alittle arrow on the edge of the map showing you the heading. Anyway, a neat little program to add to your toolbox. |
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Posted: 7/20/2008 12:17:08 PM EDT
[Last Edit: ar-jedi]
[#45]
I want a cheap, easy to use radio with long range... what do each of the following items have in common? –– unicorns. –– lower taxes. –– honest politicians. –– cheap, unlicensed, easy to use radios with long range. answer: none of them exist. so, if you are about to start a thread along the lines of the following... Originally Posted By xyz:
I am looking for suggestions on capable, 2 way communications that would be used primarily if the SHTF given that cell towers are not working, or just for use when traveling outside of cell coverage. I know from experience that the FRS and GFRS radios are complete crap. I am setting my budget at around $100 to $130 a radio. I want something with at least 10 mile (real miles, not line of sight) capability (if at all possible), handheld configuration (compatible with a base station add on later on), uses standard batteries (AA, C, whatever), and "somewhat" secure(in that Joe Blow cant walk into wally world, pick up a blister pack radio, and hear my communications) Originally Posted By xyz:
I was thinking at work to day if TSHTF How would people communicate? I have 2 radios from work so I would plan on giving one to my friend or fiance, but regular walkie talkies are good for what 100-500 yards on a clear day? I have tried the ones that say they are good for 3 miles and they don't work within a half a mile. Originally Posted By xyz:
I am not into cb radios or talking on ham radios. I really don't like to talk unless face to face. but i do know that i do need to be able to communicate or hear what is going on in the world and surrounding areas during shtf situations. so what are my options to cover this? Originally Posted By xyz:
I want a radio that doesnt require any license, gets 40-50 mile range in any terrain, and oh yeah, it has to be really cheap too. Originally Posted By xyz:
I wanna have more range than these junky little handheld radios you get at cabelas and dicks sporting goods for use when hunting or any situation where i might be further apart from someone i need to communicate with like a hunting buddy or whatever Originally Posted By xyz:
Looking for some suggestions on reliable, good walkie talkie type radios that could be found fairly cheap for SHTF type scenario. Just something the local like minded people could buy now and be able to talk in that kind of scenario. Like for a scouting party. Multiple radios on the same frequency or multi frequency radios. Older, used, whatever...as long as they work. Something I can find on Ebay? Originally Posted By xyz:
A few of us locals are taking steps to be ready if and when internet and cell phone comms go out. Can anyone recommend a good portable 2-way radio with a 20-mile range? Not looking for the Ham radio or anything with a huge antenna. Looking for something fairly reliable for mainly sporadic reports of things happening in our AO and to possibly arrange rally or bug-out points. ... the answer is "it's not straightforward." your options are, in approximate order of increasing cost, complexity, and performance:
Originally Posted By JBlitzen:
Depends on your budget, and on what sorts of communication are utilized in your area. Here are some good, and scattershot, rules of thumb to get you started: A good dual band ham radio can usually be modded to pick up, let's say, 80% - 90% of local communications, and transmit back on maybe 20% - 75%. Of course, your local police station may be in that last 10%, with a digital trunking system or something. You really have to know what's around you. A good scanner can usually pick up 90% - 100% of local communications, though it can't transmit at all. A mobile radio with a good antenna will always transmit better than a handheld, even if the handheld has a good antenna, because mobile radios usually support much higher power output. A mobile radio and a handheld radio, both attached to antennas of identical specs and positions, will usually receive equally well, since reception isn't really power based. As a corrolary of those two points, if you want to transmit rather than just receive, even (or especially) just in emergencies, then you want to focus on mobile or base radios, rather than handheld radios. The advantage over handhelds is at least an order of magnitude. The cheap Icom mobile in my truck maxes out at 55 watts, my yaesu handhelds max out at 5 watts. AM/FM broadcast bands are difficult to both tune into with any one ham radio, as they're so far apart on the RF spectrum. A good $10 am/fm radio will fill that hole in your listening needs. Local communications are usually VHF or UHF, which are, basically, line of sight, and work like FM broadcast radio. If you can see the antenna tower, you can hear the station. If there's a building in the way, you probably can't. Dual band usually refers to support for the 2 meter and 70 cm ham radio bands. 2 meter (144-148 mhz) is in the VHF range, and 70 cm (420-450 mhz) is in the UHF range, though it's not correct to say that 2 meter IS vhf or that 70 cm IS uhf, as the VHF and UHF ranges include a whole lot more than just those two ham bands. Thus, "dual band" isn't the same as "vhf/uhf". But, it's kinda close, and a lot of radio activity occurs within 50 mhz of one of those two bands. 800mhz has some public safety stuff (and a lot of the trunking public safety stuff), 200 mhz has a tiny bit of unencrypted military stuff, but most of what you'd actually want to listen to, except trunking public safety, will be within range of a dual band radio. Triband usually includes those two bands as well as 1.25 meters, which is kind of an odd, small, and low power band, which isn't used for a whole lot, and which isn't surrounded by much of anything interesting. Kinda, not much point. Quad band usually includes the same bands as a triband (2m, 1.25m, and 70cm), as well as 6 meter, which is an interesting band right on the edge of VHF, almost to HF. It's possible, under ideal conditions, to make long distance transmissions on the 6 meter band. Doesn't happen much, but it's very cool when it does. You certainly can't count on it for emergency use, though. There's some more interesting stuff around the 6 meter band than around the 1.25 meter band, but not a lot. Really kind of a niche band. One nice advantage is that quad band radios will sometimes support AM broadcast reception, and will often support FM broadcast reception. FM is around 100 mhz (when you tune in to 101.3 Warm Black Dude's Voice Cat Lady Radio, you're tuning to 101.3 mhz), which is usually out of reach of dual or triband radios as it's significantly lower than the designed 144.0 mhz lower limit. AM is around, seriously, 1 mhz. When you tune into 1180 WHAM Rush Beck News Radio, you're tuning in to 1.180 mhz. Note the decimal place. That's why you seldom find both of those bands on the same radio. The AM antenna has to be shoehorned in around all the other complicated shit, somehow without it being interfered with, and the FM broadcast band is in an engineering dead zone smack between the intended reception and transmit bands. Long distance communications are usually HF, which is weak enough that it can bounce off of our ionosphere and return to earth, rather than penetrating the ionosphere. That works like AM radio (which is actually medium frequency, lower even than HF, though there is a ham band there) (160 meters), where you can often hear stations at night that are not just counties but states or even countries away from you. And yes, standard HF ham radios can transmit at the same distances, although usually with lower power. One problem is that HF requires... patient... antennas. Which is to say, large antennas. Another problem is that HF requires a lot of power, since you're sending that signal way the hell up into lower earth orbit, bouncing it off of energy, and then sending it way the hell back down again, 1500 miles away. Bit more difficult than sending a cell phone signal to a cell tower 3 miles away. Thus, you never really see any portable HF radios. They're all mobile (designed to run off of high capacity vehicle batteries) or base (designed to run off of dedicated battery banks or AC power). Shortwave, AM, and HF, all work almost identically. CB is in that group, too, although CB equipment is legally so limited in power and capability as to be irrelevant, unless you happen to be trying to talk to someone with a CB, in which case it's the only way to fly. So, to fill out your communication niche, to listen to just about all communications, and transmit back on as many as possible, you'd want a mobile or base HF radio, a mobile or base VHF/UHF radio (possibly combined), a dedicated scanner or a very wideband VHF/UHF ham radio, and a simple AM/FM pocket radio for thsoe bands. To give you an idea of what that would cover: All ham frequencies All shortwave frequencies (listen only, with emergency transmit) All CB frequencies (listen only, with emergency transmit of dubious success) Aviation band AM broadcast band FM broadcast band Analog TV band NOAA/All Hazards frequencies FRS/GMRS frequencies All unencrypted public safety frequencies and bands Most unencrypted government frequencies and bands Most unencrypted military frequencies and bands (not satellite or ELF or stuff, of course) Most unencrypted private frequencies and bands (again, not satellite or whatever) Ambulances Police Fire Snowplows Stormchasers/Skywarn/RACES storm spotting Taxi services Buses Tow trucks Unencrypted 900mhz cordless phones Space shuttle International Space Station Amateur radio satellites Unencrypted federal agencies Unencrypted Air Force One Railroad Marine (boats n stuff) Coast guard Limited CB Things you wouldn't get: Military and commercial satellite frequencies and bands Encrypted communications Cell phones A couple other odds and ends. A special note about the Skywarn line in the above list of capabilities: many if not most tornado warnings originate from unencrypted ham radio transmissions from qualified storm spotters. If you have any interest in, or concern about, local tornadoes, hurricanes, or other severe weather, it is essential that you have the capability to monitor these transmissions, usually somewhere in the 2 meter band (144-148mhz). You will receive information about developing storms several minutes before the weather guy on TV does. Now, if you only had one radio per car, and you wanted to be able to get in touch with your wife, I would recommend a mobile radio with a good antenna for each. Handhelds are radically less effective than base or mobile radios, though of course are the only real option when outside of vehicles and away from a base station. If you can get mobile radios that support crossband repeat, that enhances your capabilities a little, by extending the utility of your mobile radios to a line of sight perimeter around the vehicles. A member of this forum was able to use that capability, after a hunting accident, to call for help while outside of cell phone calling area. He transmitted from his handheld radio, which relayed/repeated through his distant vehicle's mobile radio, which was able to reach someone who was able to alert the authorities and convey his location and status. If you can get mobile radios that support HF, that's really cool, and really fun, but adds nothing to your local capabilities, while compelling you to use a more complicated antenna system on the vehicles. On the other hand, *some* dual band VHF/UHF handheld ham radios make decent little scanners on their own. They can't track trunking conversations, but they can get pretty close, and can pick up most everything else. I like my FT-60R's for that purpose, though quad band radios have wider receive and transmit capabilities. Unfortunately, I'm not aware of any quad band radios that can run on high power from internal alkaline or lithium batteries. Additionally, the extra spectrum access really doesn't cover much of anything, except a small public safety band that isn't often used, and one or two other little things. My setup is an FT-60R handheld dual band as a portable radio/scanner, with an IC-208H mobile dual band VHF/UHF in my truck, and an IC-706MKIIG mobile HF/VHF/UHF as a base station usually packed in a pelican case. I started with the mobile radio, and I'm glad I did. I've never tested the range on it, but I can hit repeaters from 15 miles away in a city with no signal loss whatsoever. It can also pick up nearly all of the local public safety frequencies. As you can see, all of this kinda flies in the face of affordability. My starting radio was about $300, I think. And it doesn't support crossband repeat. A crossband repeat capable mobile radio would run somewhere around $400. A suitable antenna would be $50 to $75. Appropriate cable would be another couple bucks. Installing it is a chore, but you can do it yourself. Not much more difficult than installing a new car stereo and speakers and stuff. Almost any car audio installer will be happy to install ham equipment for a couple bucks. The Yaesu FT-8800R would probably be ideal for that purpose. If you want to go cheaper, and are only interested in communication with your spouse, and listening to other people, but never, ever, even if your spouse is on fire, being able to communicate to people you hear, then you could go with a single band mobile radio in each car, like an FT-1900R ($140 at universal radio) or an IC-2200H ($160), again with $40-$60 antennas each, for about $200 - $250 each car. Then get a portable trunking scanner for a little under $200, like a radio shack or uniden or something, to give you that listening capability. If you want to go even cheaper, then you can do handheld radios, like FRS/GMRS blister packs, but they tend to universally suck. They're okay if you're in a car following your spouse, but if the two cars get separated, because one gets lost, then you might easily wind up fucked. Unfortunately, handheld ham radios don't fare a whole lot better. There are unavoidable limitations when you compress a power supply and antenna into a device you can clip on to your belt. While it's true that you can plug handheld amateur radios into vehicle mounted antennas designed for handhelds (assuming the appropriate impedence; you probably can't pull that trick off with a cable and antenna designed for a mobile radio, since I believe they're 75 ohm, rather than 50 ohm that handhelds expect), you're still only transmitting at 5 watts max, and that's going to give you trouble. But, an FRS/GMRS blister pack set can be a good way to start feeling your way into radio communications. They're also usually much easier to use than ham equipment, because their capabilities are so very limited. That can make them more appealling to disinterested spouses. To give you an idea of what ham radios are capable of, if the above doesn't suggest it, consider these examples: 1. Severe storms are approaching your area. You set your portable ham radio to scan between the skywarn RACES repeater frequencies of three different counties; yours and two upwind of you. You listen to the storm spotters and the national weather service talk to each other about what they're seeing in person and on radar. You hear about a tornado sighting when it's five miles away. Two minutes later, the guy on the TV in front of you finally mentions that there's a tornado warning, but you already had that information, and had called your kids in from the yard. 2. You're out hunting, and you fall from your treestand and break your leg. You're unable to walk, three miles from your vehicle, twenty miles from town, and you can't get cell phone reception, so you request help via your portable ham radio, through your vehicle's powerful crossband repeat radio, to an area ham radio operator, who calls an ambulance for you. This, as mentioned elsewhere in this post, is basically what happened to a forum member here. 3. I go to a river lock for fun. Boats approach the lock. I take out my FT-60R, set it to smart search the marine band, and put it back on my belt. Two minutes later, I take it out again, and flip through the three results it found. One's a beacon, I can't figure out what the second one is due to there being no current traffic, but the third is the marine frequency that the lock uses to communicate with boats. I leave the radio on that, and listen in as the boats go through the lock cycle. If I had any reason to, I could press the transmit button and speak to both the boats and to the lock operator. Doing so would violate FCC rules, as the radio is not certified to transmit in the marine band. However, FCC rules also state that, in an emergency, I can use any damned means necessary to obtain help, which means that, if I fell down and broke my leg behind a bush, and I couldn't get cell reception and nobody responded to shouts, I would be legally permitted to hit that transmit button. Mundane, but a good example of the technical capabilities. 4. You swerve to miss a deer on the road. You end up running off the road into a tree, receiving light wounds in the process. The road isn't used much, it's six miles to a road that is, and you have no cell reception. Calling for help on your mobile radio obtains no answer from the local repeaters or the simplex emergency frequency. You scan through some public safety bands and immediately come across a state trooper communicating to his dispatcher about a traffic stop a couple miles away. You hit the transmit button and the dispatcher hears you. You inform them that you're a licensed amateur radio operator in a serious emergency. Maybe they yell at you, but they also send help. One last thing: it's important to remember that this is a broad overview. The capabilities and limitations of different radios within the same class, even if made by the same manufacturer, even if in the very same model series by that manufacturer, can and do differ *WIDELY*. On the universal radio site, in the mobile amateur transceivers category (we call radios like these ham radios "transceivers", as they can both "TRANSmit" and "reCEIVE", as opposed to your bedside alarm clock radio, or a shortwave radio, or a scanner, all of which only receive), I can see maybe four or five out of the 20 or 30 models that would be appropriate for casual and emergency use. For instance, digital radio is almost completely useless for your purposes, and that's what the more expensive radios usually are for. Also, the ability to modify a radio to receive, and, particularly, to transmit, outside of its intended capabilities, is vital. There are some very good radios around that simply can't be modified to have extended capabilities. That means that you're sitting there, listening to a car accident victim's screams, and listening, over the radio, to two police officers chatting on their intercar frequency at, whatever, 162.5 mhz, but you cannot talk to them because your radio only transmits between 144.0 and 148.0 mhz, and you can't raise any amateur radio operators in that band. When you see some of the Icom and Yaesu radios get mentioned, like the FT-60R, the VX-7R, the VX-6R, my IC-706, and some others, those can be modded very extensively. My 706 can essentially transmit on pretty much any frequency between 1.6 mhz and 54 mhz. Forget bands, it'll give me its best shot on literally any frequency in that range, with just a few patches for phase problems or whatever. Of course, power output and signal quality will degrade as you wander away from the designed specs, but it's a hell of a lot better than a "no tx" warning on the attempt. VHF/UHF are usually more restricted in capability due to engineering problems, but you can still open those radios up quite a bit, if they're designed for it. Other variations can be signal quality, reception quality, scanning capabilities (the Yaesu radios have a smart search capability that's breathtaking in its utility), power supplies (the FT-60R can run maxed out on humble AA's, while the VX-7R monster can only do so on internal rechargeable batteries with their logistical complexities, or on complicated external battery cases and straps; mobile and base radios are much thirstier for power, and require serious thought to their power needs, using RC, golf cart, or car, batteries), design ruggedness, interface complexity, cooling requirements, antenna connectors, mic/earphone connectors, etc. You definitely don't want to buy a radio just because the price is right, or because it looks cool. You really need to carefully review the specifications and accessories, research available mods, and read the reviews of that radio at http://www.eham.net/. Then, because those eham guys have their own interests, you'd want to come here or to a forum like zombie squad, where we're more conscious of the specific problems related to emergency use, and check with us. ps: Originally Posted By GlockTiger:
Stop looking for the quick fix, easy way out. This board is about preparedness. Actually preparing for something usually involves a little time up front. There's no quick fix in building a BOB or BOV or gardening or canning or investing or defensive training –– why must there be one for communications? You showed foresight by recognizing the need to communicate. Now that you have some direction on the subject, don't give up because you might have to invest some thought into it to achieve your objectives. We have an excellent learning environment for the topic of communications from a preps perspective –– don't shortchange us or yourself by throwing in the towel because you're intimidated by a topic that is new to you. |
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Posted: 7/20/2008 12:17:22 PM EDT
[Last Edit: ar-jedi]
[#46]
Amateur radio for preppers... contribution from pilotman: Q. I'm looking for a solution for emergency communications from a preparedness standpoint. Is Amateur Radio the solution? A. Possibly. If you're willing to take some time to learn and experiment, you will probably find amateur radio a welcome addition to your preparedness plan. Q. That doesn't sound terrible. What do I need to buy in order to communicate with (whoever I want to communicate with)? A. If you're expecting a one size fits all "emergency communications kit, just add people you want to talk to" package, you are out of luck. What you need depends on many, many variables. Part of the process here is to be able to create a system that works best for you, how to set it up, and how to use it. Yes, you get to engineer your own system for your particular needs. If you're looking at this with preparedness in mind, this knowledge is invaluable. Q. OK, I'm still interested. How much? A. The answer here depends on what exactly you want to do. However, I would say a minimum of $200 is required. On the other end of the scale, you can be well equipped for $1500-$2000 if you do your research and purchase carefully. Q. That doesn't sound too bad. Can I just buy everything and stash it away? A. To be very blunt, if you're not willing to accept amateur radio as at least a part time hobby, I would say that it's not for you. Most amateur equipment is not "plug and play", and getting everything to work correctly requires a bit of study, practice and experimentation. To use an analogy, it's not like buying a fully assembled computer, rather it's more like figuring out what components will work for your desired application and putting everything together yourself. Neither are extremely difficult, however both require something of a commitment to learning. Q. Ok, so how much involvement? A. As with anything else preparedness related, familiarity with your equipment and supplies is essential. Regardless of what the advertisements and specs say, the only way to know how your communications system will work in real life is to use it. Getting on the air and making contacts lets you know exactly what your equipment will do. Things like building and setting up your own antennas let you see and experience the theory behind everything. I personally became involved as a way to expand my knowledge of electronics, and I've enjoyed that along with other facets of the hobby. The people you will meet and talk to have very diverse reasons for their involvement (spoiler: many hams are preparedness minded) -- something that comes as a surprise to many entering what is largely seen by the public as a "nerd" hobby. Q. I want to be able to communicate securely. What about encryption? A. The short answer: The FCC prohibits encrypted communications using the amateur spectrum. |
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Posted: 11/6/2008 8:56:50 PM EDT
[Last Edit: ar-jedi]
[#47]
Reserved
ar-jedi |
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Posted: 10/15/2009 10:33:31 PM EDT
[Last Edit: Paul]
[#48]
Reserved
ar-jedi |
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Posted: 8/5/2011 5:41:16 PM EDT
[Last Edit: ar-jedi]
[#49]
PLEASE DON'T POST REPLIES IN THIS THREAD!!! folks, if you have a specific question or concern about the FAQ just IM me, or start a thread in the Ham Radio forum. thanks much. ar-jedi |
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KY, USA
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Posted: 5/27/2019 12:02:56 AM EDT
[Last Edit: M60forever]
[#50]
Does anyone have a tech/ general study guide they are not using?
Edit: sorry for posting in this thread. I should have read . apologies for not following directions. |
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) to other more SF related things. Some of their stuff is more for a non SF audence, but it's worth looking around. I downloaded every PDF they list, so I will have extra redaing material 
