We know you talk to yourself on the repeater.
Every GMRS repeater uses two frequencies: one to receive your signal (the input) and one to retransmit it (the output). The difference between these two frequencies is called the offset. Understanding offsets is essential for programming repeaters into your radio.
A repeater can't transmit and receive on the same frequency simultaneously — its own powerful transmission would drown out incoming signals. By listening on one frequency and transmitting on another, the repeater can receive and retransmit at the same time, giving you real-time communication through it.
On GMRS, the input frequency is always 5 MHz above the output frequency. When you program a repeater, you enter the output frequency (what you listen to) and set your radio's offset to +5 MHz. Your radio then automatically transmits 5 MHz higher.
Remember: You listen on the output and transmit on the input. Your radio's offset setting handles the math — you just need to make sure it's set to +5.000 MHz with the duplex direction set to positive (+).
| Channel | Output (Listen) | Input (Transmit) | Offset |
|---|---|---|---|
| 15R | 462.5500 MHz | 467.5500 MHz | +5 MHz |
| 16R | 462.5750 MHz | 467.5750 MHz | +5 MHz |
| 17R | 462.6000 MHz | 467.6000 MHz | +5 MHz |
| 18R | 462.6250 MHz | 467.6250 MHz | +5 MHz |
| 19R | 462.6500 MHz | 467.6500 MHz | +5 MHz |
| 20R | 462.6750 MHz | 467.6750 MHz | +5 MHz |
| 21R | 462.7000 MHz | 467.7000 MHz | +5 MHz |
| 22R | 462.7250 MHz | 467.7250 MHz | +5 MHz |
In CHIRP, these fields are labeled "Frequency" (output), "Duplex" (+), "Offset" (5.000000), and "Tone" / "rToneFreq." See Programming with CHIRP for a walkthrough.
If your offset is missing (set to simplex), you'll transmit on the output frequency — the same frequency the repeater transmits on. The repeater won't hear you because it's listening on the input frequency. If you accidentally set a negative offset, you'll transmit 5 MHz below the output, which is outside the GMRS band entirely. Double-check your offset direction is set to positive (+).
Channels 15-22 can be used in both simplex mode (direct radio-to-radio on a single frequency) and repeater mode (with the +5 MHz offset). When you see "15R" or "channel 15 repeater," it means the repeater pair. When you see just "channel 15," it typically means simplex on 462.5500. Make sure your radio is set to the correct mode for how you intend to use the channel.