Squelch Settings Overview (RT-880)

Noise 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.