Posted: 6/26/2008 12:51:24 PM EDT
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Let me preference this thread with; I know how these questions sound. Please believe me that I would never do anything illegal, am a law abiding citizen, but am curious. Okay i got a few questions that research (my googlefu might be weak) didn't answer: mostly devil's advocate questions: 1: If you are transmitting on VHF xxx.xxx, and an outside party knows that you are transmitting, how hard is it for them to "capture" the freq/conversation? (ie: If force Recon team A is using vhf xxx.xxx and is discovered by tango charlie, can tango charlie quickly figure out what freq force recon A is using and listen in?) 2: what's the deal with "codes?" i know that they are "strictly prohibited" unless sending to a space station, but why? and what are the consequences of doing so? (ie: userid1 calling userid2, userid1 standing by. userid2 calling userid1 go ahead with message. userid1 calling userid2 message as follows: Alpha Alpha one one niner); alpha alpha one one niner being the code. 3: who "regulates" ham frequencies? is there some central station that monitors every channel/freq? i guess for now it's just those two. however as more come to mind i'll use this thread instead of creating a couple of them. |
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
have at it. ar-jedi |
| so in response to your response of article 1 your simplified answer (and yes i'm a lamen that's why i'm asking for clarification) is that unless the opposing force knows that your using radios (and i'm not talking frs or gmrs), and unless they bring in the $$ equipment that they would not easily be able to "track and counter" your signal? |
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. ar-jedi |
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If you are are not causing big trouble, there is not going to be someone coming to DF you. If you interfere with someone's communications as AR-Jedi has demonstrated, then someone will complain and someone (FCC) will come looking. If your code phrase was "bring the watermelon", who is going to make anything of that. It is like wearing a tactical vest to the shopping mall versus a golf shirt. I have a bank of UHF frequencies programmed in my radios with mixed 440 and GMRS. If I tell my tac-group to go to bank 6 channel 11, then someone monitoring doesn't know where to look. All of my group are hams. However, high tech radio direction finding gear can locate you in seconds on any frequency. If you have seen law enforcement vehicles with the four antennas on the roof, then you have seen RDF (lojack) stuff. Incidently, a couple of local police officers got into trouble about 15 years ago using keypad programmable radios. They picked a "private" channel and were chatting on it. Turned out to be a neighboring state's county sheriff's repeater input. Are you asking about illegal use of Marine radio or unlicensed amatuer operations in a non-TEOTWAWKI situation? I would shy away from this and get gear that you can test/use on a regular basis without having to look over your shoulder. It is available and not expensive. Your group will have much better communications capability and will be familiar in its use. RS |
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Like i said, i was playing devil's advocate and trying to learn things i didn't already know. There is NO INTENT to perpetrate the above mentioned situations. On a side note, i really need to get down to the red cross next month and meet some locals. and get set up to take my test. so does my brother and a couple of our other buddies. |