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A repeater is an amateur radio station that receives a signal on one frequency and simultaneously retransmits it on another, usually from an elevated location with a good antenna. This extends the range of handheld and mobile radios far beyond what direct (simplex) communication can achieve. Repeaters are the most common way amateur operators communicate on VHF and UHF, and they form the social backbone of many local amateur radio communities.
A repeater system consists of a receiver, a transmitter, a controller, a duplexer (or cavity filters), and an antenna — typically located on a hilltop, tall building, or communications tower.
The basic process:
The difference between the input and output frequencies is called the offset (or shift). Standard offsets vary by band and region:
| Band | Common Offset |
|---|---|
| 2 metres (144 MHz) | ±600 kHz |
| 70 cm (430 MHz) | ±5 MHz |
| 1.25 metres (222 MHz) | -1.6 MHz (North America) |
| 6 metres (50 MHz) | ±500 kHz or ±1 MHz |
Whether the offset is positive (you transmit higher than you receive) or negative (you transmit lower) depends on the specific repeater and where it sits in the band. Repeater directories and your radio's programming will indicate the correct offset.
Most modern repeaters require your transmission to include a sub-audible access tone before they will retransmit your signal. This prevents interference from other signals on the same frequency.
A low-frequency tone (67.0–254.1 Hz) transmitted below the audible range along with your voice signal. The repeater checks for this tone and only opens when the correct tone is present. Common tones include 100.0 Hz, 88.5 Hz, 103.5 Hz, and many others. You may also see CTCSS referred to as "PL" (Private Line, a Motorola trademark) or "tone squelch."
Similar to CTCSS but uses a low-rate digital code instead of an analog tone. DCS codes are three-digit numbers like D023, D071, or D754. Some repeaters use DCS instead of or in addition to CTCSS.
To use a repeater, you need to know three things: the output frequency, the offset direction, and the access tone (CTCSS or DCS). These are published in repeater directories.
Several resources help you find repeaters in your area:
To call on a repeater, key up (press the PTT button) and say your callsign, optionally followed by "listening" or "monitoring":
"VK3ABC listening"
Wait a moment. If someone is available, they will respond with their callsign. If you want to call a specific person:
"VK3XYZ, this is VK3ABC"
When two or more stations are talking, wait for the courtesy tone (a short beep or tone between transmissions) and then say your callsign. The other stations will acknowledge you and bring you into the conversation.
Most repeaters emit a brief tone after each transmission drops. This serves two purposes: it confirms the repeater received your signal, and it provides a gap for other stations to break in. Wait for the courtesy tone before transmitting to avoid "doubling" (transmitting at the same time as another station).
Repeaters have a timeout timer (typically 1–3 minutes) that cuts off the transmitter if someone transmits continuously for too long. This prevents the repeater from being tied up by a stuck microphone or a single long-winded transmission. Keep your transmissions under the timeout limit. If you need to talk longer, release the PTT briefly to reset the timer, then continue.
The most common type. They receive and retransmit standard FM voice signals. Most handheld and mobile VHF/UHF radios work with analog FM repeaters.
These use digital modulation for voice communication:
Multiple repeaters connected together via the internet or dedicated radio links to create wide-area networks. Examples include IRLP (Internet Radio Linking Project), EchoLink, AllStar, and the various DMR/D-STAR/Fusion networks. These systems allow a signal received by one repeater to be rebroadcast by all connected repeaters, potentially spanning entire countries or continents.
Some radios can function as a personal crossband repeater, receiving on one band (e.g., 2 metres) and retransmitting on another (e.g., 70 cm). This is sometimes used by mobile operators to extend the range of a handheld radio, with the mobile radio acting as a relay.
Most operators store repeater frequencies in their radio's memory channels rather than manually entering the frequency, offset, and tone each time. There are several approaches:
If you are interested in operating your own repeater, there are several considerations: