CW tests ended years ago

Well, except for those of us who have nightmare flashbacks of trying (and failing) to pass the 20wpm test

On topic, I'll help out as I can with answering questions.

Learning of course, that is why i encouraged to read thru once, maybe twice if it didn't stick.

I can see how some could focus on the the mathematical questions; which were very few on the actual test that I took last month. I was hoping to encourage them to begin to get the test in their heads and not stumble on what could maybe be 2 or 3 questions max on the test.

Yes the "math" is an integral part of the process, but I wouldn't want that particular chapter of the book to scare anyone off.
It was the evil math that kept me at bay from 1998-2011, with fears of failing (and laziness in regards to learning). Finally said screw it, did best I could to retain, and passed-easily (couldn't believe how easy and wanted to kick myself for putting it off for so long).

That's all, the simplicity of the actual test maybe isn't stressed enough, and it's the thought of that test that prolly keeps most from getting past the thought of considering HAM to actually getting the ticket.

ar-jedi: if this post isn't constructive, lemmie know and I'll delete.

this is a common complaint –– why would anyone use these damn decibel units?

decibels are employed both to ease the manipulation of measurements which have an extraordinarily large span of values, and allow simple addition/subtraction to take the place of complicated multiplication/division.

but first, understand that seeing "dB" by itself represents a CHANGE –– a relative value –– and not an absolute value. in order for there to be a dB result there must be two values: a reference value, and a measured value. the measured value is expressed relative to the reference value. this is an important concept.

for example, an antenna manufacturer might say "this is a 6dB gain antenna."

your question should be "6dB relative to what?".

their answer might be "oh, we mean 6dBd, or 6dB relative to a dipole". or it might be "oh, we mean 6dBi, or 6db relative to an isotropic point source". note that 0dBd = 2.15dBi. hence, antenna vendors almost always state the dBi value, since it is a higher value it looks "better" on a glossy advertising sheet.

because "dB" is always a relative value, engineer types developed a shorthand way of demonstrating what the reference is as part of the expression. the way this is done is as a suffix to dB, as i showed above with "dBd" and "dBi". dB(x) is simply a measurement relative to (x). typically, related to radio gear, you will see (x) as "m"=(milliwatt), W=(watt), uv or u=(microvolt), and sometimes mv=(millivolt).

with RF measurements, using dBm is very common for stating a power level, and using dBuv is very common for stating a voltage level.

in one's head, one translates "dBm" to mean "dB's referenced to a milliwatt". always remember that dB is a relative value –– question should always be "relative to what?" if it is not explicitly stated.

again, read "dBm" as "dB's referenced to a milliwatt". and so on for dBW and dBuV, etc.

to convert between dBm and watts, use

dBm = (10Log10(milliwatts))
or
Watts = 10((dBm - 30)/10)

0dBm = 1mW
3dBm = 2mW
6dBm = 4mW
10dBm = 10mW
20dBm = 100mW = 0.1W
30dBm = 1000mW = 1W
33dBm = 2000mW = 2W
36dBm = 4000mW = 4W
and so on.

ergo, every added 3dB doubles the power. you can also learn some rules of thumb which will become second nature... in decimal terms, 10dB is 10x, 20dB is 100x, and 30dB is 1000x. a 30dB attenuator, for example, diminishes the output power by 1/1000 of the original.

note that dB measurements can be negative as well (this reinforces the concept that it is a relative, not absolute, measurement). take a 1W (30dBm) signal. put it through a 40dB attenuator. result? -10dBm, which is .1mW. note the ease of doing calculations this way. otherwise, you have 1W / 10000 = 0.0001W. which looks nice, because we are using nice round numbers. try it with 0.5W and 15dB of attenuation.

homework assignment:
(1) what is the power output, in dBm, of a 50W transmitter?
(2) what is the power output, in W, of a 50dBm transmitter?
(3) what is the power output, in dBW, of a 1mW transmitter?
(4) a 5W transmitter feeds a 6dB antenna. what is the ERP?
(5) a 10dBm transmitter feeds a 3dB antenna. what is the ERP?

ps#2
note the computational ease of 5 versus 4.

the cases shown above are specific because we are using a known reference point, say 1 milliwatt (0dBm). the general case is that the reference could be any power level, so the following applies:



the result is in dB and is the difference between the two powers.

ar-jedi

(1) what is the power output, in dBm, of a 50W transmitter?
50W = 10 x log10 (50W/1W) = 17 dbW

then to convert from dBW to dBM you can either add 30dB, so 17dBw = 47dBm

/or/ redo the calculation using 1mW as the reference instead:

50W = 10 x log10 (50W/0.001W) = 47 dBm.

(2) what is the power output, in W, of a 50dBm transmitter?
50dBm = 10 ^ ((dBm - 30)/10) = 10 ^ (50-30)/10 = 10 ^ 2 = 100W

(3) what is the power output, in dBW, of a 1mW transmitter?
1mW = 0dBm, and 0dBm - 30dB = -30dBW (simple way!)

(4) a 5W transmitter feeds a 6dB antenna. what is the ERP?
5W = 10 x log10 (5W/1W) = 7dBW; 7dBW + 6dB = 13dBW ERP.
13dBW = 10 ^ (dBW/10) = 10 ^ (13/10) = 10 ^ 1.3 = 20W ERP

let's do a sanity check –– we know every 3dB doubles the power. we started with 5W. 3dB more is 10W. 3dB more again is 20W. looks good.

(5) a 10dBm transmitter feeds a 3dB antenna. what is the ERP?
10dBm + 3dB = 13dBm ERP. 13dBm - 30dB = -17dBW ERP.
-17dBW = 10 ^ (dBW/10) = 10 ^ (-17/10) = 10 ^ -1.7 = 0.02W ERP = 20mW ERP

another sanity check –– we know every 3dB doubles the power. we started with 10dBm, that's 10mW. we added 3dB of antenna gain. that doubles it and gets us to 20mW. looks good.

that help any?

ar-jedi

Hi, my wife & I are both prepping for our first exams.

I’ve been lurking on ar15.com off & on for years but this thread has finally encouraged me to “sign up” even though I don’t own an EBR. Living in Illinois I opted instead for a lever-action in .308.

ar-jedi recommended defining the problem to be solved first before expanding to other interests. A good suggestion for both engineering as well as ham, SHTF prep, etc.

Our primary drive towards ham radio is being able to communicate during normal times.
We live in a rented house on a farm in rural area with more cows than people for neighbors. While my old ICOM FRS radios are good enough for when I’m back in the fields/woods that’s the extent of their practical usage and they EAT triplets of AA batteries. For our location cell phone coverage is iffy between distance and the tin roof. When I’m at work I’m 30 miles away. When she’s at work she’ll be 50 miles from the house, 30 miles from my work and on the other side of the Mississippi River.

Our secondary goal is to be able to communicate during not normal times.
We have had tornados hit within 20 miles of us to the north, east, west and southwest of us in the last 2 weeks. Ice storms are not unusual in this area. Though our home is unlikely to flood, there is a distinct possibility of being cut off by flooding. And during sustained heavy rains the basement is a poor shelter option because it is prone to wetness and even inches of standing water.

In between normal times and needing help ourselves, I look forward to volunteering to assist others. Its part of who I am. Eagle Scout/camp staff/scoutmaster in the past. Some SAR/K-9 SAR training.

BTW: I know how you move a barrel of whiskey that is too big to wrap your arms around and too heavy to move. You open it up and have a toast to good friends. Then by the time you and all your friends that have come around to also toast you and other good friends before you know it the barrel will be easy to move by whoever is still standing. :)

I’m trying to prepare for both the tech & general license in one sitting. My wife thinks she is going to have a problem keeping the electronics parts straight well enough to feel confident about the tech exam though I think that we are both going to need general to meet some of our goals. I am a computer geek (30+ yrs) with a lot of telecomm/datacomm experience. She is more “language arts” type.

I’ve been practicing using hamexam.org. She has been reading “Now you’re talking” 5th ed. My weaknesses are in: 1-antennas; 2-frequency modes and etiquette. What shape lobes you get from different types of antennas, how long and pointed which way, etc. And remembering when should I be using USB/LSB or AM vs FM depending on freq and am I suppose to be shifting by 600 khz and is that up or down.

Thx for db lesson already.
GrinningWolf

You're not the only one with an "Advanced" callsign


No state EBR ban in IL, just the Chicago area local restrictions. Plenty of EBRs and EBR manufacturers in IL.


I haven't reviewed the current test elements, so a specific question might be helpful. In general, an antenna element radiates perpendicular to the element, increasing in directivity - ie, concentrating the signal in one direction - until the element gets up to 5/8 wavelength of the frequency in use. Once the element is longer than that, the main lobe of signal skews away from perpendicular and starts going toward the end of the element. Any element more than 1/4 wavelength (monopole, 1/2 wave dipole) will have minor signal lobes in addition to the main lobe. That's simplified, for a single element antenna.... let me know if you have specific questions.


Previous answer covered a lot of it... one thing to remember on the frequency shift is that you use those shifts on VHF/UHF bands only when using repeaters, not for simplex communications. The band plan will probably seem hopelessly complicated at first glance, it might help to think of it in terms of subbands of repeater outputs, and the complimentary subbands 600kHz away of repeater inputs, with simplex frequencies or other uses in between.

EBR ban: no there isn't currently. But there almost was, SB10. And yes, I was then a marcher at IGOLD. After 20 years of living in NJ IL almost seems like firearms paradise. But it still doesn't take long to figure out that the political powers that be still want to ban all guns, but will be happy to start with ones that have things that go up and little wedges of metal that could be used to hang pointy things. Since I was shopping when SB10 was actively in play I looked at my alternatives, surveyed the firearms landscape and decided that either a level action or bolt action that could handle 5 or more rounds in either 45-70 or .308/7.62 do what I was looking to do. Hunt deer or boar in Mo or defend people at home when nothing else I had would be more appropriate. And so I found a Savage 99D.
And its purtty to boot.

[hum, pic not showing up. But it does have a nicely carved stock and forearm.]

Thx for the antenna info. I didn't ask specific test questions because I am trying to understand not just choose the correct answer. Thats also why I'm not as worried about the General pool changing soon. We had hoped to be ready to ready to test at a local hamfest the other weekend at Lewis & Clark but life had other distractions for us. But we are going to get there. We are going to get licensed and we are going to get equiped before we take a long drive out to Seattle area this Aug/Sept timeframe.

Understanding antennas is important to me. My CB experience (going back to analog tuning knobs & vacuum tubes) does not begin to prepare someone for the antenna choices of ham. With the variety of vehicles I have, even there no one antenna is going to do it all from a mobile point of view. (Dodge Calibur - VW Vanagon - Suburban - 40' skooly)

While we talking antennas - polarization. Lets make it simple and then lets go into exceptions.
I put a vertical whip on a 2M mobile. Is that going to give me horizontal or vertical polarization? I've been trying to relate this to my vague recollections of right hand/left hand rule days of EE classes, but those were 30 years ago.
I string a wire between the trees in the backyard (using balun & antenna tuner for SWR adjustment) will I have horizontal or vertical?
Note: questions T3A03 & T3A04 are about polarization.

BTW: has anyone successfully used a cattle fence wire for an antenna? AFTER pulling the plug on the power that is! Actually, since it is DC... And I don't want to be chasing cows any more than I already have to.

GrinningWolf

Vertical, then horizontal, as previously posted is correct. The right hand/left hand rule you are recalling is the relationship of the electric and magnetic fields... signal polarization is referring to the electric field.

Most common antennas are "electric antennas" so it's easy to tell the polarization just from the appearance of the antenna. Feedpoint feeding an antenna element, is that element vertical or horizontal, that's what the radiation will be. For something like a "quad" or a loop, look at where the feedpoint is - on a quad, feedpoint at the bottom is horizontal, at the side for vertical. Slot antennas, magnetic field antennas and the like get confusing as the polarization is opposite from what they appear (that right hand/left hand rule) but you won't deal with those very often.

Well I use cattle fence wire (aluminum) as my typical wire antenna material, but not in a cattle fence configuration

approximately the GDP of Sweden. that should get you started!

seriously, though, this is more or less the same as "how much should i set aside for guns?" –– the answer in that case is how far/fast/accurate you want to shoot, etc. you can get a used G19 for $300 and you have a gun. you can also purchase a new Accuracy International AWM in .338 Lapua –– and the scope mounts alone are going to run you $300.

here are some "rough guidelines" that assume new, modern equipment.

HT's, or Handy Talkies –– small, portable, self contained radios that you can put in your jacket pocket. primarily used in conjunction with repeaters, but can be used simplex.
2m VHF or 70cm UHF FM HT: $100 to $150
2m/70cm VHF/UHF "dual band" FM HT: $175 to $300

Mobile radios –– designed to be mounted in a vehicle but are commonly used in the house as fixed stations as well. used in conjunction with repeaters, or used simplex.
2m VHF FM mobile: $125 to $200
2m/70cm VHF/UHF "dual band" FM mobile: $275 to $500

HF radios –– designed for fixed station or portable use. in this category there is HUGE variation in capabilities, and therefore in price as well.
6m-160m all mode HF radio with AF DSP: $600 to $900
6m-160m all mode HF radio with IF DSP: $800 to $1200

"Shack in a box" radios –– all bands, all modes,
2m/70cm + 6m-160m all mode HF radio with AF DSP: $700 to $1200
2m/70cm + 6m-160m all mode HF radio with IF DSP: $1000 to $2000

"Contester" radios, HF radios designed specifically for optimum performance.
6m-160m all mode HF radio with IF DSP and front panel bandscope: $1500 to $10000

now then, antennas...
mobile VHF/UHF installation, requires NMO, magnet, or lip mount AND aerial: $50 to $200
fixed station VHF/UHF installation, requires coax downlead and aerial: $100 to $500

for HF the antenna "system" usually consists of the antenna itself, the downlead, and a tuner. there is a HUGE variety of HF antennas available (and you can also construct them yourself). you can spend $50 or $50,000 on HF antennas, and no i am not making that last number up.
tuner: $100 to $500
fixed station HF, wire antenna, e.g. OCF dipole: $50 to $200
fixed station HF, vertical antenna, $100 to $750
fixed station HF, beam antenna and associated rotor: $500 to $2000

ar-jedi

Hey gentlemen,
I'm currently studying to get my Technician license and started off scoring mid 50's on the practice tests. After a couple days reading I am up to 80%-90%. Next test in my area isn't til July so I've got plenty of time to prepare, may even go for the General. The study guides are great but I would like to learn more than just how to pass the test. There is a local club here that I'll be checking out soon.

I'm not quite sure how I want to start out, as far as equipment. I'm thinking a mobile setup would be best since I travel (and move) a lot.

My Dad (W6DX) has been urging me to get into Ham since I was a teenager and I am finally getting interested. I will talk to him this weekend and get his input. He may even have some gear I could try out before buying.

Thanks guys for the outstanding info here.

Hope this will be some encouragement if anyone is struggling. Last night we had the largest turnout we'd had in a while and everyone passed one or more exams. Now for the encouraging part. One of the guys taking his Tech exam failed. He said he wasn't surprised. This was his 10th attempt since 1993 (I guess he gives up between exams). We encouraged him to try again and that we didn't mind waiting. Well, he passed with flying colors the second time. The point is that he never gave up and soon he'll finally be able to get on the air.