//RADIO//TECH//ETC-T2

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by disinfoniacs #69 & #1

squelch, tones, etc

>>>>

tldr

• Squelch control mutes the receiver audio when no signal is present, effectively eliminating the continuous static noise.
• Repeaters use either CTCSS (Continuous Tone-Coded Squelch System) or DCS (Digital Coded Squelch) tones transmitted from the radio to "key" open the squelch and retransmit the signal
• Improper transceiver offset or missing CTCSS/DCS tone can cause a failure to transmit on a repeater.
• Access to repeaters is also dependent on tone, offset, color codes, and special codes (e.g. DTMF audio tones, talk group ID).
• A linked repeater network is a network of repeaters that transmit received signals to one another (e.g. PAPA system in California).

in depth

Squelch control is an important aspect of ham radio communication. It allows you to >mute the receiver audio when no signal is present, which eliminates the static noise that would otherwise be heard continuously. Squelch is frequently used by repeaters to eliminate stray signals and only retransmit signals that are meant to be heard, an important feature as due to their optimal location they tend to receive many unwanted signals.

To achieve this, repeaters use either CTCSS or DCS tones that are sent from the radio. CTCSS stands for Continuous Tone-Coded Squelch System and is a subaudible tone that is transmitted along with normal voice audio. This tone acts as a “key” that opens the squelch of the receiver and allows the repeater to retransmit the signal.

On the other hand, DCS, or Digital Coded Squelch, uses digital codes instead of subaudible tones to open repeaters. This method is used more frequently in metropolitan areas and operates in a similar manner to CTCSS. Both CTCSS and DCS serve the same purpose of helping to ensure that only intended signals are retransmitted through a repeater.

Access to repeaters is dependent on several factors including offset and tone. If you are unable to transmit on a repeater, it may be:

• Improper transceiver offset.
• The repeater may require a proper CTCSS tone from your transceiver.
• The repeater may require a proper DCS tone from your transceiver.
• (For testing purposes, all these answers are correct.)

In addition to offset and tone, other features and systems in ham radio may require special codes for access. DMR (Digital Mobile Radio) repeater systems use "color codes" which much match and access to a digital repeater's "talk group" requires programming the radio with the group's ID or code. Touch-Tones, also known as DTMF audio tones, are used for signaling repeaters or other equipment. You'll be able to find the proper settings needed to connect in most online repeater information repositories.

Some repeaters are linked becoming a "repeater network" which will transmit signals received by one repeater to all the others. An example of a popular linked repeater network is the PAPA system in California which allows ham radio operators to communicate up and down the coast from their homes.

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