What a repeater is, and how to work one
A handheld radio on a hilltop can be heard for a hundred kilometres. The same radio in a valley, or in a car, might not reach the next town. A repeater is the fix: a station on high ground that listens on one frequency and retransmits everything it hears on another, in real time.
Two frequencies, not one
Because a repeater transmits and receives at the same moment, it cannot use one frequency for both — it would deafen itself. So every repeater has an output, which is what you listen to, and an input, which is what you transmit on. The station is named by its output: a repeater "on 145.750" means you hear it there.
The gap between the two is the shift, sometimes called the offset. On the 2 m band in most of the world it is 600 kHz; on 70 cm it is usually 1.6 MHz in Region 1 and 5 MHz in the Americas. The sign matters: a shift of −600 kHz means you transmit 600 kHz below the frequency you are listening to.
Why your radio needs three numbers
- The output frequency, which you tune to.
- The shift, which tells the radio where to transmit.
- The access tone, which tells the repeater you are a licensed operator and not interference.
Get the first two right and you will hear the repeater but never open it. That is the single most common reason a new operator calls and hears nothing back.
Opening a repeater
Listen first — for long enough to be sure a contact is not already in progress with a gap in it. Then give your callsign. On a quiet repeater, "IU4ABC listening" is enough; there is no need to call CQ, which belongs on the HF bands.
Leave a beat between pressing the transmit key and speaking: the repeater needs a moment to come up, and the first syllable is otherwise lost. Leave another beat between overs so someone else can join, which is a courtesy and, on a linked system, a requirement.
When nothing happens
- Wrong or missing access tone — the usual cause.
- Shift set the wrong way round, or disabled.
- Out of range: a repeater is line-of-sight, and terrain wins over power every time.
- The machine is off the air. They do go down, and directories go stale.