How to Use Them
If you are new to ham radio the best practice is to simply listen to a repeater frequency for a while. It won’t be long before you see how the locals are using it. You rarely hear anyone call CQ on a repeater. It is more common to simply announce your call sign and say “listening” or “monitoring”. Anyone who hears this and wants to chat will call you right away.
Sometimes you will hear a net being conducted on a repeater. Nets are discussed in another article on this site. You should become familiar with the nets on the repeaters that you use. Your participation is usually welcome but special protcol applies.
How They Work
Repeaters listen on one frequency and re-transmit on another. The difference between the frequencies is called the offset. There are not enough frequencies in each amateur radio band to provide every repeater with its own unique frequency. So frequencies are repeated but only at a distance that should prevent one repeater from interfering with another. This system is not perfect and sometimes a repeater will re-transmit a signal that was intended for a different repeater or system. As a solution to this problem repeaters are often set up to listen for a sub-audible tone, called a PL (private line) tone. This tone is also referred to as CTCSS (continuous tone coded squelch system).
Programming Your Radio
To use a repeater you need three pieces of information:
- The repeater’s transmit (your receive) frequency
- The offset which is generally given as just + or –
- The PL tone (if any)
Follow your individual radio’s instructions to place these three values into the memory of your radio and you are ready to use the repeater. The user manual for many of the most popular radios are available in our knowledge base. Radios are most easily programmed using computer software and a USB connection to the radio. Most can be programmed using the dials and buttons on the radio itself. Some do both.
If the transmit frequency is lower than the listening frequency this is called a negative offset. If the transmit frequency is higher than the listening frequency this is called a positive offset. By convention, the difference between the frequencies for VHF (2 meter) repeater is 600 KHz. For UHF repeaters the difference is 5 MHz. Most radios know this and allow you to simply enter + or -.
The PL/CTCSS tone works two ways. Your radio must transmit the PL tone or the repeater will not re-transmit your signal. Your radio might separately accept a “Receiver Tone”. If you enter it then your radio will not put any signal through to the speaker unless the tone is detected.
The American Radio Relay League (ARRL) publishes an annual Repeater Directory listing all repeaters on all bands state by state. You can also find a repeater directory in your smart phone’s app store.
Repeater Book is an online repeater directory that you can use to search by city and state or by proximity to a location