GMRS License

GMRS Frequencies

Repeater Information

GMRS Repeater Programming

GMRS repeaters work by receiving weak radio signals on one frequency (input) and re-transmitting them at higher power on a different frequency (output), effectively extending communication range far beyond direct radio-to-radio (simplex) limits, especially in hilly or urban areas, by using strategically placed antennas (often on high ground) and handling a standard 5 MHz frequency offset automatically for users

How the process works:

  1. Simplex vs. Duplex: Standard radios use simplex (same frequency in/out), while repeaters use duplex (different frequencies in/out).
  2. Frequency Offset: GMRS repeaters use a standard +5 MHz offset; your radio transmits on the higher frequency (e.g., 467.550 MHz) and listens on the lower frequency (e.g., 462.550 MHz).
  3. Signal Reception: A user transmits on the designated repeater channel (e.g., Channel 15), which sends the signal to the repeater’s input frequency (462.550 MHz).
  4. Rebroadcasting: The repeater, placed on a tall tower or hilltop, receives this signal and rebroadcasts it on its output frequency (467.550 MHz) at higher power.
  5. Extended Range: Other users within the repeater’s large coverage area (potentially 20-50+ miles) hear the transmission on the lower frequency, even if they are miles apart.
  6. Tones (CTCSS/PL): Repeaters often use specific tones (like CTCSS or PL) to prevent interference from simplex users on the same frequency, requiring your radio to send the correct tone to “open” the repeater. 

GMRS Tone Codes

GMRS tone codes (CTCSS/DCS) work by adding an inaudible, low-frequency tone (like a sub-audible whistle) to your radio’s transmission, acting as a “key” for receivers; radios set to the same tone will “unlock” and pass the audio, while others on the same frequency ignore it, reducing interference on busy channels, especially with repeaters, but they don’t encrypt conversations. 

How it works

  • CTCSS (Continuous Tone-Coded Squelch System): Sends a constant, low-frequency tone (e.g., 100 Hz) with your voice.
  • DCS (Digital-Coded Squelch): Sends a digital code instead of a tone.
  • The “Key”: When you press the Push-to-Talk (PTT) button, your radio sends your voice plus the selected tone/code.
  • The “Lock”: Other radios on the same frequency, programmed with the same tone/code, recognize it and open their speaker (squelch) to let your audio through.
  • The “Filter”: If a radio isn’t set to your tone, its speaker stays silent, filtering out your transmission and others’ chatter.