Repeater Offset Calculator
Enter the repeater's published (output) frequency and this calculator applies the standard US offset to show your transmit (input) frequency: −100 kHz on 10 m, ±600 kHz on 2 m (below 147 MHz is usually minus, 147 and above plus), −1.6 MHz on 1.25 m, and ±5 MHz on 70 cm. Modern radios auto-apply these — this tool is how you verify what they picked, and what you enter when they don't.
Enter the repeater's published (output) frequency — try 146.940 — and we'll compute the input your radio must transmit on.
Every repeater listens on one frequency and transmits on another — the gap is the offset, and it's standardized per band so radios can guess it automatically. When the radio guesses wrong (or you're programming manually, or a listing looks odd), thirty seconds here settles it.
New to how the input/output dance works? Read repeaters explained first. Hunting for machines worth programming? Start with finding local repeaters.
How repeater offsets work
A repeater receives your signal on its input frequency and simultaneously retransmits it on its output frequency. Directories list the output — that's where you listen. Your radio must transmit shifted by the offset: press PTT and it jumps to the input, release and it returns to the output. The shift happens automatically once the channel stores the offset direction and size.
The offset exists because a repeater's receiver and transmitter run at the same instant on the same antenna system; separating the frequencies (and filtering hard between them with cavities called duplexers) is what makes that possible.
Standard US offsets by band
These conventions cover the overwhelming majority of US machines:
| Band | Repeater range | Standard offset | Direction convention |
|---|---|---|---|
| 10 m | 29.5–29.7 MHz | 100 kHz | Minus |
| 6 m | 51–54 MHz | 500 kHz or 1 MHz | Varies regionally — check listings |
| 2 m | 144–148 MHz | 600 kHz | Below 147 MHz: minus · 147+: plus (regional exceptions exist) |
| 1.25 m | 222–225 MHz | 1.6 MHz | Minus |
| 70 cm | 420–450 MHz | 5 MHz | Varies by coordination; plus is common in the low 440s |
When a listing disagrees with the convention, the listing wins — regional frequency coordinators occasionally assign non-standard splits to squeeze machines into crowded spectrum.
Don't forget the tone
The offset gets you to the right input frequency; the CTCSS tone gets the repeater to listen. Most machines require a sub-audible tone on your transmission, listed alongside the frequency (e.g., "103.5"). Program it as Tone (encode) — not TSQL — and you're set. The full story, including the complete tone table and DCS codes, is in CTCSS & PL tones explained.
Reverse: listening on the input
Most radios have a "reverse" function that swaps you onto the repeater's input momentarily. Two practical uses:
- Hear who's nearby: a station you copy on the input is within simplex range — you could move off the repeater and talk directly (146.520 or another simplex channel).
- Troubleshoot access: if a friend can't open the machine, listening on the input tells you whether their signal is arriving at all.
It's also the polite diagnostic when the repeater seems busy: check whether the conversation is actually local before assuming the machine is dead. Range logic for the simplex fallback lives in how far can a ham radio transmit.
Programming the whole thing per channel
A complete repeater memory channel stores five things: receive (output) frequency, offset direction, offset size, tone mode, and tone value. Keypad entry works for one machine; for a real list use CHIRP — it imports straight from RepeaterBook and writes all five fields per row. The walkthrough is in program a Baofeng with CHIRP, and it applies to nearly every beginner radio.