Presented by Steven Hanson, KJ7NYE
Credit where credit is due:
- “Anatomy of a Repeater” – Steve Ford, WB8IMY, QST, May 1995
- “Repeater Terminology” – ARRL
- ARRL Handbook for Radio Communications (2025 Edition)
- Practical Antenna Handbook – Joseph J. Carr & George W. Hippisley, W2RU (2011)
What Is a Repeater?
A repeater is like a radio “relay station.” It listens for a signal on one frequency and re-broadcasts it on another, allowing your voice to travel farther than your radio alone could manage. Repeaters are usually located in high places like hilltops, towers, or tall buildings, giving them wide coverage.
If you’ve ever talked to someone miles away on a handheld radio, chances are a repeater was helping you out.
Types of Repeaters
🔁 Half Duplex (Parrot Repeater)
- RX & TX on the same frequency
- Records and plays back what you just said
- Often used for testing or very short-range comms
📶 Full Duplex
- RX & TX on different frequencies (an offset)
- The most common type in amateur radio (especially on the 2-meter band)
🔀 Cross-Band
- Receives on one band (e.g., 2 meters) and transmits on another (e.g., 70 cm)
- Handy for events when using a handheld radio and needing extended coverage
Anatomy of a Simple Repeater
- Receiver (RX) – Listens for incoming signals
- Transmitter (TX) – Re-broadcasts those signals
- Controller – The “brains” of the system, handling timers, IDs, and more
- Antenna – Often shared for RX and TX
- Duplexer – Lets one antenna handle both RX and TX at the same time without interference
Duplexers Explained
Duplexers are filters that keep the repeater’s transmitter from overwhelming its own receiver.
Types:
- Band-Pass – Passes a narrow slice of frequencies, blocks others
- Band-Reject (Notch) – Blocks a specific frequency, passes others
- Hybrid – Combines both for maximum isolation
Linked Repeaters
Sometimes repeaters are “linked” together to create even larger coverage areas.
Why Link?
- To cover wide areas (e.g., from Wilderness Ridge to Boise)
- For emergency communications across multiple regions
Linking Methods:
- Local – Multiple repeaters at one site sharing a controller
- RF Linking – Using another radio frequency (including microwave bands)
- Internet Linking – Using IRLP or AllStar to connect worldwide
Common Terms You’ll Hear
- Courtesy Tone – A beep after someone stops talking, letting others know the channel is free
- Kerchunking – Briefly keying your mic to see if the repeater is on (frowned upon unless testing)
- CTCSS / PL Tone – A sub-audible tone used to access certain repeaters and reduce interference
- DTMF – Tones sent by your radio’s keypad to control or link repeaters remotely
- Offset – The difference between the repeater’s receive and transmit frequencies
- Sensitivity – How well a receiver can pick up weak signals
- Selectivity – How well a receiver ignores unwanted nearby signals
Standard Repeater Offsets (ARRL Band Plan, 2025)
| Band | Typical Offset |
|---|---|
| 6 meters (50–54 MHz) | -500 kHz, -600 kHz, or -1 MHz (varies) |
| 2 meters (144–148 MHz) | ±600 kHz |
| 1.25 meters (222–224 MHz) | -1.6 MHz |
| 70 cm (420–450 MHz) | ±5 MHz |
| 33 cm (902–928 MHz) | -25 MHz |
| 23 cm (1240–1300 MHz) | -20 MHz |
Troubleshooting – “I Can’t Get Into the Repeater!”
- Check Your Offset
- Make sure your radio’s +/– setting matches the repeater’s
- Verify Your CTCSS/PL Tone
- Wrong tone = repeater won’t hear you
- Disable Receive PL Tone
- If the repeater doesn’t use it, it may block you from hearing others
- Monitor Input Frequency
- Use your radio’s monitor function to see if your signal is getting in
- Check Power & Antenna
- Low power or high SWR can cause poor performance
In Summary
Repeaters are one of the most powerful tools in ham radio—literally extending your reach and connecting communities. By understanding how they work, the terminology, and how to access them properly, you’ll get more enjoyment and capability out of your license.
So next time you key up on a local repeater, you’ll know exactly what’s going on behind the scenes.
