Making Sense of What You Hear- Part 1, by Hal2000

Knowledge is power. At least that is how the saying goes. For the sake of this discussion let us consider knowledge to be synonymous with information. When it hits the fan, where do you plan to get your information?

I want to make you aware of all the information available via radio. I don’t mean the AM and FM radios in your home and car. These will most likely be spewing forth whatever the government line is for the day. I am talking about police scanners, shortwave radios, and amateur or Ham radio.

I know some are going to think that there is nothing to hear on police scanners now days, but please bear with me. There has been a tremendous evolution of police scanners over the last five to ten years. Shortwave radio has remained pretty much the same, but Ham radio is currently undergoing a slow change over from analog to digital communications. I want to make you aware of these changes and how you can benefit from them.

This was intended to be a short primer for preppers who are not familiar with police scanners, shortwave radios, and Ham radio, including a high level overview of what these radios do and how you can use them in your prepping. It soon became apparent that a lot of background information would need to be included, and before long this blossomed from a small article to a very large article consisting of many parts. Without the added detail, it would not be of much value.

I tried to stay as non-technical as I could, but if you are going to play with radios you will have to understand some very basic things. My intent is to make you aware of what is currently available and how you can use it to your advantage. If you want more detail, there is plenty of information on the Internet. However, before you can search the Internet you have to know what to search for, right? I will provide search keywords throughout the article where you can obtain much more detailed information.

For those who are already familiar with this information, don’t be too critical. As you know, there is a lot more detail that I could have included, and while a few things might be generalized I intend for this article to be a starting point for those who currently know nothing about the topic.

Some Basic Definitions

In order to understand what you will be able to hear and where you will hear it, you need to have a basic understanding of frequency ranges, different modulation types, and where they are most prevalent.

Khz – Kilohertz

This is a measurement of frequency. 1 kilohertz equals 1 thousand hertz (or cycles). Your favorite AM station might be 980 on the dial, which means 980 Khz.

Mhz – Megahertz

This is a measurement of a frequency. 1 megahertz equals 1 million hertz (or cycles). Your favorite FM station might be 101.1 on the dial, which means 101.1 Mhz.

HF – High Frequency

This describes the range of frequencies from 3.0 Mhz to 30.0 Mhz.

VHF – Very High Frequency

This describes the range of frequencies from 30.0 Mhz to 300.0 Mhz.

UHF – Ultra High Frequency

This describes the range of frequencies from 300.0 Mhz to 3 gigahertz (Ghz).

CW – Continuous Wave

This is the earliest form of communication. Basically you rapidly turn your transmitter on and off, forming the dots and dashes that make up the morse code alphabet. This mode takes up very little frequency or bandwidth.

AM – Amplitude Modulation

This is the oldest form of voice communication and why it is sometimes referred to as Ancient Modulation. You will hear this primarily on the standard AM broadcast band, International shortwave broadcasts, and aircraft communications. It consists of three components– a carrier and an upper and lower sideband. This mode takes up quite a bit of bandwidth.

SSB – Single Sideband

This was an improvement on AM modulation. The AM carrier and either the upper or lower sideband are removed from the signal before being transmitted. This mode takes up more bandwidth than CW but less than AM. You will almost never hear it referred to as SSB but rather USB or LSB depending on which sideband has been removed from the transmission.

FM – Frequency Modulation

This mode modulates the frequency and can take up a lot of bandwidth. Wide band mode is used for FM broadcasting while the narrow band mode is used in VHF and UHF communications.


This is the most common mode of voice communication. Your voice is used to modulate a transmitter, and there is no digital processing of the signal.


This is the new wave sweeping pretty much all VHF and UHF communications. Your voice is digitized and then sent via the transmitter. Before being transmitted, the bits representing your speech can be rearranged resulting in an encrypted signal unable to be heard without being unscrambled by the receiver.


The most important radio for a prepper is a Police Scanner. My first police scanner was a Regency 10 channel crystal controlled scanner, circa the early 70’s. After a few trips to Radio Shack, I had crystals for the local police, fire, and highway patrol. It was simple. Plug the crystals into the radio, turn it on, sit back, and listen to the action. But as we all know, nothing stays the same. Change is inevitable and as it turns out expensive.

Next came scanners that didn’t require crystals. You could simply program the frequencies you needed into the scanner then sit back and listen to the action. But then you began to hear strange sounds coming from the radio and you couldn’t understand as much as you did before. Welcome to scrambling technology. With the progression of technology came changes to voice communications. The powers that be began to scramble their conversations so the general public couldn’t understand them. Was this done to keep you from using a scanner in the commission of a crime or because of technical improvements? It was probably a little bit of both. Soon you realized that you can’t hear all the stuff you used to hear, so you lived with what you could hear or took up another hobby.

About this same time technology continued to improve and simplex gave way to repeaters. An explanation is due at this point. Simplex communications means that the dispatcher talks on one frequency and the officer responds on that same frequency. It sounds simple, and you may ask how else would they talk to each other. The problem with simplex is that while the dispatcher may be transmitting with lots of power and an antenna in a high location, your vehicle transmitter has a much lower power level and a small antenna. The farther away you get from the dispatcher and as you go up and down hills, you and the dispatcher may or may not hear each other all the time. There are lots of dead spots or areas where one person can not hear the other.

So what do you do? Along comes something called a repeater. This device is a combination transmitter and receiver. It receives on one frequency and retransmits what it hears on another frequency. The dispatcher and officers transmit on frequency A and listen on frequency B. Why do you want to do that? The advantage of a repeater is that you can locate the repeater in a central location and mount the antenna very high. This helps eliminates dead spots and greatly improves the coverage area.

As the coverage area improves, more people with scanners can hear more. So you begin to hear even more scrambled communications as the powers that be become even more paranoid. Soon you realize that you can’t hear as much police and fire activity as you used to hear, but something else happens about the same time. Even though repeaters are more expensive than simplex communications, the greater coverage area begins to interest other types of users. Businesses, TV and radio stations, traffic reporters, school districts, trash trucks, public transportation, and lots of other people who want or need communications begin to set up and use their own repeaters. These are known as non-public service operators.

What we have now are lots of repeaters with lots of information being passed, and only the police and fire comms are being scrambled. Everything else is in the clear and easily understood on your scanner.

So how can we take advantage of this? Granted, the really juicy conversations on the police repeaters may be scrambled, but there is a tremendous amount of information on the other repeaters. How many bus drivers, cab drivers, school bus drivers, trash truck drivers, traffic reporters et cetera know anything about OPSEC? Virtually none! If there is a major traffic incident or fire or robbery or car chase or anything else happening, you may hear some of it on the police channels, but you will hear a lot of uncensored information about it on the non-public service repeaters. It’s information you may want to know if you are bugging out or just want to know what is going on around your neighborhood.

At this point in time everything is cool. You have all the police and fire repeaters programmed in your scanner as well as all the non-public service repeaters, and you are hearing lots of stuff and are happy as a clam.

But then everything changes. Along come cell phones. What do cell phones have to do with scanners? The technology behind how cell phones work is adapted to public service communications. As you drive along talking on your cell phone your signal is transferred from cell to cell. Hence the name cell phone. A cell is a location with transmitters, receivers, antennas, and computers that handle your phone call for a very small area. This small area is known as a cell. As you can imagine, there must be a very large number of cell sites in order to allow you a continuous conversation as you drive from point A to point B. You are right.

Let’s back up a little at this point and talk about the radio spectrum. The radio spectrum is a finite resource. There are only so many frequencies available for simplex, repeaters, and cell sites. So the problem becomes how do you pack more and more people into a finite resource? For public and non-public service users, the answer is something called trunked radio systems.

This is where your programmable analog scanner is relegated to the trash heap. (Don’t throw it away yet. We can still use it, and we’ll talk about how later).