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You bought a radio, got your license, tuned to a repeater channel, and you can hear people talking. You key up, say hello, and... nothing. Nobody responds. The repeater doesn't retransmit you. This is the single most common frustration for new GMRS operators, and it almost always comes down to one missing setting.
The repeater is ignoring you because your radio isn't sending the correct access tone. Most GMRS repeaters require a specific sub-audible CTCSS tone (sometimes called a PL tone) to be transmitted along with your voice. Without it, the repeater hears your signal but refuses to retransmit it.
You can hear the repeater just fine because it transmits on an open frequency that any radio can receive. But getting the repeater to listen to you requires sending the right tone. Think of it like a locked door with a keypad - you can hear people talking inside, but you can't get in without the code.
CTCSS stands for Continuous Tone-Coded Squelch System. It's a very low-pitched tone (below what you can hear) that your radio transmits whenever you key up. The repeater listens for this specific tone before it will retransmit your signal. There are 38 standard CTCSS tones, ranging from 67.0 Hz to 254.1 Hz. Each repeater uses one specific tone, and you need to match it exactly.
You might also see this called:
Some repeaters use DCS (Digital-Coded Squelch) instead. Same concept, different technology. See CTCSS and DCS Tones Explained for the full details.
You need two pieces of information for any repeater: the frequency and the tone. Here's where to find them:
A typical repeater listing looks something like:
The exact steps vary by radio model, but here's what you need to set on the repeater channel:
If you're using CHIRP (free programming software), these fields are labeled Frequency, Offset, and Tone/TSQL. Set the Tone Mode to "Tone" (transmit tone only) and enter the CTCSS frequency. See Programming with CHIRP for a step-by-step walkthrough.
Common mistake: Setting the tone mode to "TSQL" instead of "Tone." TSQL requires the tone on both transmit and receive, meaning your radio will also filter what it hears. If you're not hearing anything, this might be why. For most repeaters, "Tone" (transmit only) is the correct setting.
GMRS repeaters receive on a frequency 5 MHz above where they transmit. If your radio doesn't have the +5 MHz offset set, you're transmitting on the repeater's output frequency - the repeater is listening 5 MHz higher and never hears you. Double-check that your offset is set to +5.0 MHz on repeater channels. See Repeater Offsets for the full channel pair table.
Once you've programmed the frequency, offset, and tone:
If you've confirmed the correct frequency, offset, and tone but the repeater still won't retransmit you:
For a complete troubleshooting guide, see Can't Access a Repeater?
All of this only applies to repeaters. If you're talking directly to another radio on a simplex channel (no repeater involved), you generally don't need any tone. Just set the frequency, make sure both radios are on the same channel with no offset, and transmit. Simplex channels are GMRS channels 1-7 and 15-22 without the repeater offset.
If you can hear a repeater but it won't retransmit you, the fix is almost always: look up the repeater's CTCSS tone, program it into your radio as the transmit tone, and make sure your offset is set to +5 MHz. That's it. Once those two settings are right, the repeater will hear you and you'll be on the air.