A repeater listens on one frequency and re-transmits on another, a fixed distance away. You listen to its output; your radio has to transmit on its input. That difference is the offset, and the tone is the key that opens the door.
The three numbers
| Setting | Where it comes from | Typical values |
|---|---|---|
| Frequency (output) | The repeater listing | 146.940, 444.500 |
| Offset (direction + amount) | Band convention | 2 m: ±600 kHz · 70 cm: +5 MHz (some areas −) |
| Tone (CTCSS "PL" or DCS) | The repeater listing | 88.5, 100.0, 141.3, D023N |
Offset direction on 2 metres
The standard band plan makes this mostly predictable: repeaters between 145.1 and 146.4 and between 146.6 and 147.0 use a minus offset; 146.4-146.6 and 147.0-147.4 use plus. The ChatterBack listing shows it as a sign after the frequency: 146.940− means transmit on 146.340.
On the radio
Every radio names these slightly differently. Look for:
- Duplex / Shift / Offset direction: +, − or off (simplex).
- Offset frequency: 0.600 on 2 m, 5.000 on 70 cm.
- Tone mode: "Tone" (transmit only - what you want to start) vs "TSQL" (also squelch on receive). Start with transmit-only; you'll hear more.
- Tone frequency: the number from the listing.
If you own a programming cable, CHIRP is free, supports most cheap radios, and shows all of this as a spreadsheet. Save your file. You will reflash this radio someday.
Test it without being that person
Key up for one second and let go. If the repeater is hearing you, you'll get a short burst of carrier or a courtesy beep back. That's a kerchunk. One is fine; it's how everyone checks. Five in a row is rude and, strictly, an unidentified transmission - say your callsign if you need to test again: "KI5QRT testing."
Hearing the repeater but it won't hear you? Nine times out of ten it's the tone. The tenth time it's the offset direction.