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Squelch Settings Overview (RT-880)
🕑 Added 2025-08-30 12:58:29 +0000 UTCNoise Ceiling
Description:
The Noise Ceiling sets the threshold at which external noise (ex-noise) is considered maximal. When the noise level reaches this point or above, the squelch will close immediately, without delay or exception.
Effect:
Any noise at or above this level triggers instant squelch closure.
Ensures complete silence when excessive external noise is present.
Noise Trigger
Description:
The Noise Trigger determines the threshold below which external noise (ex-noise) must fall in order for the squelch to open.
Effect:
Squelch will only open when the external noise drops below this level.
Works in conjunction with the Noise Hysteresis setting to prevent rapid squelch toggling.
Note: Refer to the Noise Hysteresis setting for additional context on smoothing squelch operation.
Squelch Level
Description:
The Squelch Level sets the S-Unit value required for the squelch to open.
Effect:
The S-Unit value corresponds to Squelch Level − 1.
Example: A setting of 4 requires the signal to reach at least S3 to open the squelch.
A setting of 1 (S0) effectively enables Noise Only mode, opening the squelch on any detectable signal.
Setting this to 0 (Off) causes squelch to be permanently open.
Noise and Signal Hysteresis
Description:
Hysteresis sets a buffer to prevent the squelch from rapidly opening and closing due to small fluctuations in noise or signal levels. Units are measured as 1 dBm per 12.
Effect:
Applies to both noise-based and signal-based squelch logic.
Introduces a difference between the open and close thresholds, reducing “squelch chatter” caused by minor variations in signal or noise levels.
Example: If the squelch opens at a certain level, it will only close when the signal/noise drops below that level minus the hysteresis value.
Squelch Throttle
Description:
The Squelch Throttle sets a minimum delay between squelch state changes, preventing rapid toggling.
Effect:
When the squelch changes state (open → closed or closed → open), the throttle ensures that no further state change can occur for the duration specified in tenths of a second.
Helps to avoid rapid squelch cycling in environments with fluctuating signals or noise.
Squelch Tail
Description:
The Squelch Tail determines how many consecutive checks must confirm that the squelch should close before it actually does.
Effect:
Prevents the squelch from closing too quickly due to brief signal drops.
Provides smoother operation by requiring consistent conditions before closing.
Note: This setting is overridden by the Noise Ceiling, which will close the squelch immediately if exceeded.
Squelch Tail Elimination (STE)
Description:
Squelch Tail Elimination (STE) is a system designed to remove squelch tails at the end of transmissions, improving clarity and reducing noise.
Effect:
Requires both parties in a communication to have STE enabled to function correctly.
Allows configuration of RX, TX, or Both elements of the system.
Typical Usage: Setting to Both is recommended for most applications to ensure full tail elimination.
nicFW's squelch cut off response is extremely quick, so this setting is only useful in very noisy environments.
Comments
Marcus Dudley
Note Squelch Tail is available from ALPHA 18 which is not yet released. ALPHA 18 also overhauls the squelch system and introduces new defaults.
John Parham
Thank you so much for the detailed explanations. I was never very clear on the settings and how these are related to each other.
