Tone Access vs Carrier Squelch

Every repeater has a squelch system that determines what signals it will retransmit. The two main approaches — carrier squelch and tone squelch — work very differently, and understanding them is key to using repeaters successfully.

Carrier squelch

Carrier squelch is the simplest approach: the repeater retransmits any signal it receives, as long as the signal is strong enough. No special tone or code is needed. If you key up on the correct frequency, the repeater opens.

• Pros: anyone can use the repeater without knowing a specific tone. Simple to set up on your radio — just program the frequency and offset
• Cons: the repeater can be triggered by interference, spurious signals, or intermod from nearby transmitters. This causes the repeater to key up and retransmit noise or garbage, which is annoying for anyone monitoring

Tone squelch (CTCSS/DCS)

Tone squelch adds a gate: the repeater only retransmits signals that include a specific sub-audible CTCSS tone or DCS code. Your radio transmits this tone continuously whenever you key up (you can't hear it — it's below normal audio frequencies). The repeater checks for this tone before opening its squelch.

• Pros: interference and random signals don't trigger the repeater. Only intentional users with the correct tone can activate it. This keeps the repeater quiet and clean
• Cons: you must know and program the correct tone to use the repeater. Without it, the repeater hears your signal but ignores it

How this affects your radio settings

When programming a repeater channel, you have several tone-related options:

• No tone (carrier squelch): your radio transmits without any sub-audible tone. Use this for carrier-squelch repeaters and simplex channels
• Transmit tone only ("Tone" in CHIRP): your radio sends a CTCSS tone when you transmit, but accepts any signal on receive. This is the most common setting for repeaters — you need the tone to key up the repeater, but you want to hear everything the repeater retransmits
• Transmit and receive tone ("T-SQL" or "TSQL"): your radio sends a tone on transmit and only opens squelch on receive if it hears the same tone. This filters out other repeaters or stations on the same frequency that use a different tone. Useful in areas with overlapping repeater coverage

A common problem

You can hear a repeater just fine, but when you key up, nothing happens — the repeater doesn't retransmit your signal. The most likely cause: the repeater requires a CTCSS/DCS tone that you haven't programmed. Your signal reaches the repeater, but without the correct tone, the repeater's squelch stays closed and it ignores you. See Can't Access a Repeater? for a full troubleshooting guide.

Which tone do I need?

Check the repeater listing on myGMRS.com, RadioReference, or our repeater search. The listing will show the required CTCSS tone frequency (e.g., 141.3 Hz) or DCS code (e.g., D023). Program this as your transmit tone on the repeater channel. For more on CTCSS and DCS, see CTCSS and DCS Tones Explained.