The need for communication security
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Many preppers foresee the need for CB radios in a crisis, but, unfortunately, using a transmitter can bring an enemy or predator to your doorstep. If you use a radio to communicate with another member of your party, anything you say can be used against you. It is even possible to locate you by homing in on your signal.
Normally, the Citizens Band channels are chaotic, with everyone speaking at once, so that it is very difficult to understand what anyone is saying. In a survival crisis, however, expect the airwaves to be much quieter, as preppers won’t be burning up their batteries for idle chatter. It will be easier to listen in on a transmission.
Any prepper who plans to use CB should be aware that each time he transmits, he advertises his presence, and if he is chatty, he will give away vital information, such as his location and plans, to anyone within range. “Anyone” may include an occupation force, a repressive government, or a band of looters.
Some preppers are concerned with having a retreat, away from it all, as a shield against whatever they see coming. Some foresee various possibilities, or scenarios, as follows:
In all of these scenarios, it is clear that the first line of defense is concealment. This means not only physical concealment but keeping a low profile by other means.
Few are aware of how vulnerable the use of radio makes them. The first, and obvious, fact is that anyone who monitors the bands becomes aware immediately that there is someone else out there. Because CB is short-range, anyone who hears a transmission knows that the sender must be within a few miles, or even within a few hundred yards.
What you say can give you away. Let’s eavesdrop on an imaginary conversation:
Mobile: “Hey, base, I’m coming in with the water.”
Base: “Okay. Come In by the Redman Road turnoff, and I’ll keep an eye out for you,”
Anyone who hears this knows that there are at least two people, that one is mobile and one is fixed, where the mobile person will be shortly, and what his cargo is. This sets up for either following or ambush.
Let’s eavesdrop again:
Mobile: “Base, I see three people in a truck coming down the road.”
Base: “Roger, I’ll send Chuck and Mike out to help. Are you still in the bushes behind the gas station?”
Mobile: “10-4.”
If the people in the truck have a CB, and are listening in, they know that they’ve been spotted, and how many they can expect to meet shortly.
Related reading: Detailed Strategies For Surviving An Ambush
The military and the intelligence services call this “traffic analysis.” It’s possible to learn a lot by listening in to unguarded conversations.
Direction-finding is another technique for locating a transmitter. As with traffic analysis, this complex of techniques finds wide use among the military. During World War II, for example, the Allies located and sank German U-Boats by monitoring their radio signals.
Radio-location depends on two techniques. Even the military’s classified equipment uses the same basic principles of signal strength and relative bearing. It’s possible to judge how close a transmitter is by the strength of the signal. Anyone who tries to find a transmitter can tell whether he’s getting closer or farther away by how loud the signal is.
Direction-finding by relative bearing depends on the fact that many antennas are directional: the strength of the signal relates to their position. Anyone who has used a television with a “rabbit ears” antenna knows how this works. Even certain types of outside antennas must be pointed toward the transmitter for the best reception.
Even an antenna not constructed to be directional receives better in one position in relation to the transmitter. A few tests with a friend operating the transmitter can show you what position gives you the best reception with your antenna. The results vary with the type of antenna, which makes it absolutely necessary to run tests on your own equipment.
Anyone who tries to locate a transmitter, unless he has very specialized equipment, will not know from which side the signal is coming, even when he finds the position that gives him the strongest reception.
He will, however, know that the transmitter is somewhere along a certain line. If he changes his position by a few hundred yards, he’ll find that the bearing is different, and he’ll be able to plot the bearings on a map, or even judge them intuitively, to find where they meet, which will tell him the location of the transmitter.
If there are two receivers, the task is easier and quicker. Each can “home in” on the transmission simultaneously with the other, which will be important if the transmission is short. Unless the person operating the transmitter is a “motor-mouth.” there may not be enough time for one person to move far enough to get a second bearing.
From this brief understanding of the ways in which your radio can be used against you, it’s possible to lay out some defensive measures to eliminate or reduce the risks.
This is the only sure defense. An eavesdropper can’t hear you If you don’t say anything. You can use your mobile phones for communication, stringing telephone wire from one site to another when you have enough wire is also an option. You can send someone to carry the message, which is usually practical because few messages are likely to be urgent.
Use the radio only for listening. You probably have already planned to do this, as in a crisis, you will depend heavily on the Emergency Broadcast System, shortwave, and other bands for your information. This has the advantage of saving your batteries, as listening uses far less power than transmitting.2.
Listen aggressively, sweeping the various channels available to you. Someone may be transmitting near you, and you’ll want to have a chance to determine whether they are friendly or hostile, and what their intentions are.
Use the same techniques that might be employed against you—traffic analysis and direction-finding. If you have two radio sets, position them several hundred yards apart, and establish phone communication between them, so that the two operators can triangulate on a signal quickly.
Prepare in advance for some rudimentary direction-finding. Find out how directional your antenna is, and if you feel that it won’t do the job, construct a simple directional one. While antenna design is a very complex subject, and designing a technically correct one requires some mathematical calculations, you don’t have to do a perfect job. For your purpose, a cheap and dirty direction finder will do.
There are several ways to make a directional antenna. One is a simple V-beam. Two feet of No. 10 copper wire, a jack, and some solder are all you need. This antenna receives best when the open end of the V points toward the transmitter.
Another is the dish antenna. This is simply a metal bowl, or floodlight reflector, with a short piece of wire in the center. Strictly speaking, this type of antenna is more suited to microwaves than the CB band, but it will work well enough.
This antenna is simply an antenna jack with a wire leading into the bowl through a threaded tube, the sort found in lamp fixtures, with about two inches of wire extending into the dish. The threaded tube shields the wire from radio signals so that the only part of it that acts as an antenna and picks up signals is the short length inside the bowl. The metal of the bowl shields it from back signals so that only the ones in the direction of the open end of the bowl will register.
Neither of these antennas is technically correct. Neither one is electronically matched to the receiver, and the stub of wire used in the dish antenna will not pick up signals very well, but both will do the job well enough.
You’ll probably find that the signal strength meter on your set is more sensitive to variations in signal strength than is your ear. The human ear judges sound in increments of ten, which are called decibels, and slight variations will be difficult to pick out.
This is especially true when listening to human speech, rather than a steady tone. The signal strength meter measures the strength of the signal and provides a visual readout, which is easier to detect as long as there is enough light to read the meter.
When you pick up a signal and get a bearing, look in both directions, as you may be getting a back signal, depending on the type of antenna you’re using. This is most likely if you’re using the one that comes with your radio. You may be able to pick out the source of the signal visually. If you can’t, you must set up a baseline, either moving along a few hundred yards or coordinating with another listener.
If you must transmit, keep it short. Remember that the longer you stay on the air, the more time you give a listener to find you. Keeping your transmissions brief is not difficult to do, as matters which require the use of the radio usually do not demand detailed explanations. If there is something that requires an extended discussion, walk, or ride over. Any emergency transmissions will be short.
Read next: Crisis Communication Advice – Ditch the cell phone (or not?)
If necessary to transmit, do it away from the home base. You might send out a party to explore the area, telling them to transmit any significant information by radio. Have the home base operator take his equipment some distance away, so that anyone trying to home in on transmissions will not find your location.
Even if you haven’t enough wire to run a landline to the transmitter, there are ways to work around this problem. Signaling by a minor, or by shielded flashlight at night, provides communication when there is a clear line of sight. Except in an emergency, you should be able to select a secondary site that offers line-of-sight.
Use the least signal strength possible to do the lob. In ordinary times, using the full power of your set is advantageous, as it enables you to achieve maximum reach and over-power interference, but if you’re concerned about possible listeners, using high power would be indiscreet.
Most transmitters have a selector switch for either high or low power. Even the cheapest walkie-talkies have telescoping antennas, which you can manipulate for minimum signal strength. Do not extend the antenna any farther than is necessary to avoid propagating your transmission unnecessarily.
As a practical matter, CB sets vary in strength, with the minimal ones having a range of perhaps half a mile under ideal conditions. More powerful transmitters, using full legal power and with good antennas, easily reach 5 miles under good conditions. Intervening buildings, hills, and other obstructions can reduce this, while transmissions over water will extend the range.
Some CBers, in violation of FCC regulations, have linear amplifiers connected to their transmitters. These can extend the range far beyond the one for which the set is designed.
Excessive propagation can be dangerous, as it extends the area in which someone can hear you. Keeping the power down will help protect you.
If you must transmit, at least avoid giving away any information about yourself, your party, and your location and plans. Using code has two purposes: to conceal information and to shorten transmission time. Often, the two purposes work together, although there are some examples of codes used only to shorten time on the air.
The police codes are a good example. During busy periods, a police dispatcher must control a number of units, and the well-known “10-codes” are a means of cutting air time. It takes a lot less time to say, “10-7,” than it does to say, “Out of service,” “10-98,” similarly is briefer than, “Am finished with last assignment.” Police codes do not conceal anything, as many people know them, and they have been published. Their only purpose is to save time.
Concealing information is not much more difficult. It is easy to make up a list of numbers to correspond with various meanings you know you’ll need. There are two points to watch when compiling a code. One is to plan to change the code often, on the off-chance that someone has been listening and has been able to figure out the meanings from the context.
As it is impossible to cover all of the possible messages you might need and still keep the code list short, you will have to transmit some messages partly in plain language, or “Clear .” For example, “97” means. “Meet me at,” but you may not have a code number for “… the church off Route 19.” Your message would then be, “97 church off Route 19.” After several of these, a listener would start to get an idea of how your code works.
Another way your code’s security might break would be human error. One party might say that he had not understood the last transmission, and the other party would repeat the message in clear. It is a cardinal error to repeat a coded message in clear, as this gives the code away, but it happens from time to time.
The second point is to avoid numbers or words that sound alike and which might either be mistaken for each other or cause the hearer to request a repeat. “14” and “40” sound-alike enough so that one or the other should be deleted from any code list.
In compiling your code, it is easy to make a list of the words and expressions you think you’ll need and to assign numbers to them. Whenever possible, try to have a code number stand for a phrase rather than an individual word. This will make the transmissions briefer, although you’ll sacrifice some flexibility.
Making up the original code list and getting copies to all who’ll need them will be relatively easy, but code changes later on, without access to a printer, will be more difficult. Unless you want to make up many code changes at one time, copy them and store the copies, which will mean weight and bulk, you’ll have to make your changes during the course of the crisis.
There are some easy solutions to this problem. The word to describe them is “superencipherment,” which means re-numbering your code. For example, you might decide that the numbers keep their original meanings, but that you’ll multiply them by two when transmitting. The listener would divide the numbers you give him by two in order to extract the meanings.
A superencipherment could be additive, also. You might simply add one to each number on the basic code list. Next week, you might add two, etc. The simplest code is the best. When you have to cope with the prospect of being overheard, one simple code for emergency use is clicking the microphone switch.
To the eavesdropper, a couple of clicks might sound like interference or a loose connection in his equipment. Of course, you can’t transmit long messages with this method, as it would then sound like Morse code and would advertise to anyone listening that someone was transmitting.
If you are posting a lookout, for example, you might require him to report in a very simple code. One-click would mean. “I see something, and will report in person to tell you about it.” Two clicks would mean “Emergency! Something dangerous coming. Get ready to fight or run.” Three clicks would mean, “I’m bugging out!” To ensure communications security for yourself and the members of your survival group, you’ll have to take a few simple precautions in advance.
Talk over the need for communication security with the members of your group. Discuss the ways in which the unwise use of the radio can compromise the safety of your group. Decide how much of your anticipated communication really needs to go out over the air, and alternative methods of communication.
Keep in mind that the need for communications security does not change much with circumstances and that while you avoid worrying about giving away your home base if you plan to be on the move, you still have to watch yourself If you don’t want everyone to know you’re coming. Once you and your group decide policy, you can start on physical preparations. If you don’t have radio equipment, get it, paying special attention to broadband receivers, as listening is more important than talking in a survival crisis.
Recommended reading: HAM Radio – A Critical Piece Of Equipment For Survival Communications
Do your tests in direction-finding, and build an antenna, if the one that comes with the equipment is not suitable. The time to get the bugs out of the equipment is now, not when the crisis strikes. Do some field tests on the practical range of your equipment, so that you’ll have an idea of how far your transmissions will carry.
Keep this in mind when planning your survival site. In a deep valley, stray transmissions will not go beyond the tops of the hills or mountains around you, in many cases, and this gives you an advantage. Practice emergency communications with your group. Compile your code list, decide on emergency procedures, and persuade the members of your group that they should be very familiar with them. Getting the bugs out of your system means paying attention to the human equation, too.
If you and your group plan your actions in advance and work out the scenarios, and the communications that you’ll need, you’ll find that there are very few situations that absolutely require the use of the radio and that most messages can wait, or be transmitted by other means.
With a lot of planning and a little bit of luck, you’ll be able to maintain total communication security by keeping radio silence. If you absolutely must transmit, you’ll be prepared to minimize your exposure, and the risk, by using the techniques of security that you’ll have practiced. That way, your radio won’t betray you.
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As to the CB direction finding antenna constructed from a metal bowl with a 2 inch wire in the center, that may work for frequencies in the gigahertz range, but definitely not for CB which is around 26-27 mHz. Otherwise a well written and informative article.
Question: Would Morse code be a better way to transmit, is it as easily detected as human speech in regards to being tracked? Perhaps using one of those children’s clickers? It seems like using a Morse Code (like perhaps five clicks means “come back quickly”) would a) lessen the chance of someone breaking the code and b) perhaps not catch someone’s attention who is listening in, as fast as hearing a voice.
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The need for communication security
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