Many preppers foresee the need for CB radios in a crisis, but unfortunately, using a transmitter can put an enemy or robber on your doorstep. If you use a radio to communicate with another member of your party, anything you say could be used against you. It is even possible to locate you by tuning in to your signal.
Usually the citizen radio channels are chaotic as everyone is talking at the same time so it is very difficult to understand what someone is saying. In a survival crisis, however, you should expect the airwaves to be much quieter as the preparers won’t be draining their batteries on idle chatter. It will be easier to overhear a broadcast.
The need for communication security
Any prepper planning to use a CB radio should be aware that they are announcing their presence each time they broadcast, and if they are talkative, they will provide important information, such as their location and plans pass it on to anyone within reach. “Anyone” can be an occupying power, a repressive government, or a gang of looters.
Some preppers are all about having a retreat, away from it all, as a shield against whatever they see coming. Some envisage different possibilities or scenarios, as follows:
– Emergency powers – During a crisis, the government declares a state of emergency and confiscates weapons, stocks of food and other resources.
– Foreign Occupation – A foreign power occupies the land and issues confiscatory decrees as sweeping as those described above. Everyone must register with the occupying army and obtain an identity card. Anyone who does not comply with the decrees will be executed.
– Looters – During a crisis, lawless gangs prey on the survivors who have been stockpiling food and other supplies. Law enforcement is ineffective, and survivors must defend themselves.
In all of these scenarios, it is clear that the first line of defence is hiding. This means not only hiding physically but also using other means to keep a low profile.
Few realize the vulnerability of using radios. The first and obvious fact is that anyone monitoring the tapes will immediately realize that someone else is out there. Because CB radio has a short range, anyone who hears a transmission knows that the transmitter must be within a few kilometres, or even a few hundred yards.
What you say can betray you. Let’s eavesdrop on an imaginary conversation:
Mobile: “Hey base, I’m coming in with the water.”
Base: “Okay. Come in at the Redman Road turnoff, I’ll look out for you.”
Anyone who hears this knows that there are at least two people, one mobile and one stationary, where the mobile person will be shortly and what their load is. This prepares either a pursuit or an ambush.
Let’s listen again:
Mobile: “Base, I see three people driving down the street in a truck.”
Base: “Roger, I’m sending Chuck and Mike out to help. Are you still in the bushes behind the gas station?”
Mobile: “10-4.”
If people in the truck have a CB and are listening in, they’ll know they’ve been spotted and how many to expect shortly.
Traffic analysis and communication security
The military and intelligence agencies call this “traffic analysis.” You can learn a lot by listening in on unsupervised conversations.
Direction finding is another technique for locating a transmitter. As with traffic analysis, this complex of technologies is also widely used in the military. For example, during World War II, the Allies located and sank German U-boats by listening to their radio signals.
Radio location depends on two techniques. Even the military’s secret devices use the same basic principles of signal strength and relative bearing. You can judge how close a transmitter is based on the signal strength. Anyone trying to find a station can tell by the volume of the signal whether it’s closer or farther away.
Direction finding by relative bearing relies on the fact that many antennas are directional: the strength of the signal is related to their position. Anyone who has ever used a TV with a “bunny ear” antenna knows how this works. Certain types of outdoor antennas also need to be pointed at the transmitter for the best reception.
Even an antenna that is not designed for directivity will receive better in a certain position in relation to the transmitter. A few tests with a friend operating the transmitter can show you what position your antenna will give you the best reception. The results vary depending on the type of antenna, so it is absolutely necessary to carry out tests with your own device.
Anyone trying to locate a transmitter, unless they have very special equipment, will not know which side the signal is coming from, even if they find the position that gives them the strongest reception.
However, he will know that the transmitter is somewhere along a certain line. If he changes his position a few hundred yards he will find that the bearing is different and he will be able to plot the bearings on a map or even judge them intuitively to find out where they meet, which tells him the location of the transmitter.
If there are two recipients, the task is easier and faster. Each can “lock on” the transmission at the same time as the other, which is important when the transmission is short. Unless the person operating the transmitter is a “motor-talker”. A person may not have enough time to move far enough to get a second bearing.
With this brief understanding of the ways your radio can be used against you, it’s possible to take a few countermeasures to eliminate or reduce the risks.
Strategies for maintaining communication security
1. Maintain radio silence.
This is the only sure defence. An eavesdropper can’t hear you if you don’t say anything. You can use your cell phones to communicate, also running telephone wire from one location to another is an option if you have enough wire. You can send someone to deliver the message, which is usually handy as few messages are likely to be urgent.
Use the radio for listening only. You probably already have this planned, as in a crisis you rely heavily on the Emergency Broadcast System, shortwave and other bands for your information. This has the advantage of saving your batteries as listening uses a lot less power than transmitting.
2. Listening
Listen aggressively and browse the various channels available to you. Someone may be broadcasting in your area and you want to be able to tell if it’s a friendly or hostile broadcaster and what their intentions are.
Use the same techniques that could be used against you – traffic analysis and direction finding. If you have two radios, position them a few hundred yards apart and establish a telephone connection between them so the two operators can quickly triangulate a signal.
3. Prepare.
Prepare in advance for a rudimentary direction finding. Find out how directional your antenna is, and if you feel it can’t do the job, build a simple directional antenna. Although antenna design is a very complex subject and constructing a technically correct antenna requires some mathematical calculations, you don’t have to do a perfect job. For your purpose, a cheap and dirty direction finder will do.
4. Build an antenna.
There are several ways to build a directional antenna. One is a simple V-ray. Two meters of #10 copper wire, a jack and some solder is all you need. This antenna receives best with the open end of the V pointing toward the transmitter.
Another possibility is the parabolic antenna. This is simply a metal bowl or floodlight reflector with a short piece of wire in the middle. Strictly speaking, this type of antenna is more suited to microwave than CB band, but it works well enough.
This antenna is simply an antenna socket with a wire going into the dish through a threaded tube like those found in lamp mounts, with about an inch of wire protruding into the dish. The threaded tube shields the wire from the radio signals so the only part of the wire that acts as an antenna and receives signals is the short length inside the dish. The metal of the shell shields the signals from behind, so only the signals towards the open end of the shell are registered.
Neither of these two antennas is technically correct. Neither antenna is electronically matched to the receiver, and the stub of wire used in the dish antenna won’t pick up the signals very well, but both do the job well enough.
You will probably find that the signal strength meter on your device is more sensitive to fluctuations in signal strength than your ear. The human ear judges sound in units of tens called decibels, and slight fluctuations are difficult to detect.
This is especially true when you hear human speech rather than a steady tone. The signal strength meter measures the strength of the signal and provides a visual reading that is easier to see as long as there is enough light to read the meter.
When you receive a signal and get a bearing, look both ways as you may get a return signal depending on the type of antenna you are using. This is most likely if you are using the antenna that came with your radio. You may be able to visually identify the source of the signal. If that’s not the case, you’ll need to establish a baseline, either by moving a few hundred yards or by coordinating with another listener.
5. Keep it short.
If you must broadcast, keep it short. Remember, the longer you stay in the air, the more time you give a listener to find you. It is not difficult to keep your transmissions brief, as matters requiring the use of the radio do not usually require detailed explanations. If there is something that requires a lengthy discussion, walk or drive over. All emergency transmissions will be short.
6. Don’t give away your base.
If it is necessary to send a message, do it away from the home base. You could send out a squad to scout the area and tell them to radio any vital information. Have the home base operator set up their equipment some distance away so anyone trying to eavesdrop on the transmissions cannot find your location.
Even if you don’t have enough cabling to run a landline to the transmitter, there are ways to work around this problem. Signalling by a minor or by a shielded flashlight at night allows communication when there is a clear line of sight. Except in emergencies, you should be able to choose a secondary location that provides a line of sight.
7. Use a weak signal.
Use the lowest possible signal strength to make the lob. In normal times it is advantageous to use the full power of your device, as this will give you maximum range and clip interference, but if you are concerned about potential listeners it would be indiscreet to use high power.
Most transmitters have a selector switch for either high or low power. Even the cheapest walkie-talkies have telescopic antennas that you can manipulate for minimal signal strength. Don’t extend the antenna any further than necessary to avoid unnecessarily scattering your transmission.
In practice, CB radios vary in power, with the smallest units having a range of perhaps half a mile under ideal conditions. More powerful transmitters, using full legal power and equipped with good antennas, easily reach 5 miles in good conditions. Intermediate buildings, hills, and other obstacles can reduce this range, while transmissions over water increase the range.
Some CB radio operators, contrary to FCC regulations, have connected linear amplifiers to their transmitters. These can extend the range well beyond what the device was designed for.
Excessive propagation can be dangerous because it increases the range over which someone can hear you. Keeping the power low can protect you.
8. Use a code.
If you must broadcast, you should at least avoid giving out information about yourself, your group, your location, and your plans. Using a passcode serves two purposes: hiding information and reducing transmission time. Often both purposes work together, although there are some examples of codes used just to reduce airtime.
The police codes are a good example of this. At peak times, a police dispatcher has to control a number of units, and the well-known “10 codes” are a means of reducing airtime. It takes much less time to say “10-7” than “Off Duty”, and “10-98” is also shorter than “I’ve finished my last job”. The police codes hide nothing because many people know them and they have been made public. Their only purpose is to save time.
Hiding information is not much more difficult. It’s easy to create a list of numbers corresponding to different meanings that you know you will need. There are two points to consider when composing a code. One is that you should plan to change the code often in case someone was listening and able to figure out the meanings from the context.
As it is impossible to cover all possible messages and still keep the code list short, some messages must be partially transmitted in the clear, or “Clear .” For example, “97” means. “Meet me in,” but you may not have a code number for “…the church on Route 19.” Your message would then read: “97 Church on Route 19.” After several of these examples, a listener would begin to get an idea of how your code works.
Another way to break the security of your code would be human error. One party could say that they didn’t understand the last transmission and the other party would repeat the message in plain language. It’s a cardinal mistake to repeat an encrypted message in plain text as it gives away the code, but it happens every now and then.
The second point is to avoid numbers or words that sound similar and that could either be confused or lead the listener to ask for a repeat. “14” and “40” sound so similar that one or the other should be left out of any code list.
When assembling your code, it’s easy to make a list of the words and phrases you think you’ll need and assign numbers to them. Whenever possible, you should try to make a code number stand for a phrase rather than a single word. This makes transfers shorter, although you lose some flexibility.
Compiling the original code listing and distributing copies to anyone who needs it is relatively easy, but later code changes without access to a printer will be more difficult. Unless you want them
making many code changes at once, copying and storing the copies, which means weight and bulk, you need to make your changes over the course of the crisis.
There are some simple solutions to this problem. The word that describes them is “superencipherment,” meaning renumbering your code. For example, you might decide that the numbers will keep their original meaning, but that you will multiply them by two when transcribing. The listener would divide the numbers you give them by two to extract the meanings.
Encryption could also be additive. You could just add one to each number on the base code list. In the next week, you could add two, etc. The simplest code is the best. If you are at risk of being overheard, a simple emergency code is to flip the microphone switch.
To the eavesdropper, a few clicks could sound like interference or a loose connection in his system. Of course, you can’t transmit long messages using this method, because then it would sound like Morse code, announcing to the listener that someone is transmitting.
For example, if you post a lookout, you could ask him to report in a very simple code. A mouse click would mean. “I’m seeing something and I’ll be in touch personally to tell you about it.” Two clicks would mean: “Emergency! Something dangerous is coming our way. Get ready to fight or run.” Three clicks would mean, “I’m off!” To ensure the security of communications for yourself and the members of your survival group, you must take a few simple precautions beforehand.
9. Get everyone on board.
Talk to the members of your group about the need for communication security. Discuss how careless use of the radio can endanger the safety of your group. Decide how much of the expected communication really needs to go over the airwaves and what alternative methods of communication exist.
Keep in mind that the need for communications security varies a little depending on the circumstances, and while you don’t have to worry about giving away your home base if you plan to be en route, you still need to be careful if you don’t want to, that everyone knows you’re coming. Once you and your group have decided on a strategy, you can begin the physical preparations. If you don’t have radio equipment, get one, paying particular attention to broadband receivers, as listening is more important than speaking in a survival crisis.
10. Testing and more testing.
Test the bearing and build an antenna if the one supplied is not suitable. The time to get the bugs out of gear is now, not when the crisis hits. Conduct some field tests on the practical range of your gear so you have an idea of how far your transmissions will go.
Keep this in mind when planning your survival location. In a deep valley, stray transmissions will in many cases not go past the tops of hills or mountains around you, and that gives you an advantage. Practice emergency communication with your group. Gather your code list, establish emergency procedures, and convince the members of your party that they should be very familiar with them. To get the bugs out of your system, you also need to pay attention to the human equation.
final word
As you and your group plan your actions in advance and work out the scenarios and communications you will need, you will find that there are very few situations that absolutely require the use of the radio and that most messages are waiting or otherwise transmitted can become.
With a lot of planning and a little luck, you can maintain total communications security by maintaining radio silence. If you absolutely must broadcast, you will be prepared to minimize your exposure and risk by using the safety techniques you have practised. This way your radio will not give you away.
