Radio Basics
Introduction
This section covers basic scanner operation and programming, simplex and repeatered radio operation, frequency allocations, and digital and trunked radio operations.
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Basic Scanner Operation
Most scanners purchased within the last 10 years are quite simple to use. Gone are the days of changing crystals to tune frequencies, manually entering frequencies just to get started, and receivers susceptible to even the most minor intermodulation and bleeding. Modern scanners have "one touch" buttons for finding active amateur, aircraft, fire, police, medical, marine, and weather frequencies. Inexpensive new scanners can follow conversations on most trunked radio systems, ensuring that when technology upgrades, you're not left without your information feed. Digital systems are still making their way onto the scene, and digital-capable scanners, while still not as affordable as analog ones, are beginning to come to market and drop significantly in price.
So, what do all of those buttons on your shiny new scanner do? Most scanner manufacturers have been good at keeping the functional use of their product the same, regardless of make or model.
Standard Scanner Buttons/Functions
| Button | Function |
|---|---|
| Scan / Man | Generally toggles between scanning the stored frequencies or sitting on one frequency. |
| Lockout / L/O | Keeps the frequency programmed, but prevents the scanner from checking that frequency when in SCAN mode. |
| Lock / Key | Locks the keypad so frequencies or settings aren't modified by accidental keypresses. |
| Program / PGM | Allows you to set frequencies to be scanned/saved. Usually the PGM button is pressed, then the frequency is entered. |
| Priority / PRI | Sets a priority channel that is monitored while scanning. This channel is tuned to even if there is active radio traffic on another frequency. |
| Tune | Allows the scanner to be tuned to a specific frequency via the Up/Down arrow buttons or numeric keypad. |
In addition to allowing you to manually tune or scan pre-selected frequencies, many new scanners also feature a signal isolation feature that quickly scans large ranges of frequencies and helps narrow down the exact frequency a station is transmitting on. Many scanners also allow you to place channels into different banks (groups) for scanning — a bank for public safety, a bank for businesses, a bank for HAM, and so on.
As always, if you're unsure about a function on your equipment, check the instruction manual or search online.
Standard Radio Operation
Now that you know how to listen to radio conversations, there's a good chance you want to know more about the radios themselves.
A radio transceiver might be a handheld (portable), vehicle-mounted (mobile), or a base station. The biggest difference between the three types is generally transmit power — mobiles and base stations will typically have a larger transmit power rating, as battery power/current is much more readily available than on a portable hand-talkie. The other major difference is the antenna: you can only do so much with a portable antenna, but vehicle-mounted/mast-mounted antennas are generally going to have a higher vantage point with fewer obstructions and provide better coverage. Higher-power radios and/or radios with better antenna setups will usually be clearer and more audible over longer distances than portables.
Radio transceivers generally have several functions, depending on the type of radio system (analog, digital, trunked) and radio brand. Just about every radio will have three basic functions: volume, squelch, and a PTT (push-to-talk) transmit button. Other functions include the ability to change channels (so one agency or group can communicate with another), an emergency ("man-down") button, a transmit power switch, fine tuning adjustments, and other features.
Simplex vs. Repeatered Operation
The most basic type of radio communication is simplex radio operation. Radios in simplex mode are generally low-powered, and transmit and receive on a single frequency. In simplex scenarios, receipt of a transmission depends on the distance and terrain between the communicating units; a central unit may sometimes need to act as an information relay if conditions aren't right. If two units on a simplex frequency transmit at the same time, different transmissions can be received by various people depending on who has a stronger signal.
Most radio users who need to cover areas larger than a few city blocks operate their radios through a repeater system. A repeater-capable radio listens for radio traffic on one frequency (the receive frequency) and sends radio communications to the repeater on another (the transmit frequency). The repeater unit, which usually has a high power output and an antenna at a high altitude relative to the surrounding terrain, works the opposite way — it listens on the radios' transmit frequency, and transmits the traffic on the radios' receive frequencies. If two units attempt to transmit at the same time, one of a couple of things may happen depending on received signal strength at the repeater: if the signal strength is similar, the repeater might repeat both transmissions at once, garbling them ("doubling"), or the unit with the stronger signal may completely "step on" the other's transmission.