Guide Audio recording gating

Guide: audio recording gating (squelch)

What it is. Gating decides when a recording is written. Without it, Record audio writes everything, including hours of silence or hiss. With Only audio switched on, the recorder behaves like a squelch: it saves only while there is sound, cuts the silence out, and keeps a short lead-in and tail so the start and end of a transmission are not clipped. It is how you leave a recorder running on an airband or PMR channel overnight and get only the calls.

Step by step

1. Tune a mode that plays sound, for example Airband or the General receiver in NFM.
2. In the diagnostics strip, tick Only audio.
3. Optionally tick Split: a new file starts after 3 s of silence, so each transmission is its own file. Without Split everything goes into one file with the silence removed.
4. Tick Keep going if you will change frequency while recording.
5. Choose the format (WAV, FLAC or MP3) and press Record audio.
6. While the gate is closed the red button reads Stop ... (waiting); when audio arrives it counts up again.

Setting the squelch first

The gate follows the audio, so the mode's own squelch matters. In Airband the Squelch slider (carrier-to-noise in dB, range -5 to 30) sets how much a channel needs to open, and Hang keeps it open for 0 to 3 s after the signal ends. Lower values open on weaker stations but also on noise; the noise floor is tracked per channel. In the General receiver use the squelch of the demodulator. If the recording fills with hiss, raise the squelch before blaming the gate.

Combining with the noise remover

The squelch and the recordings are taken after the neural noise remover, so cleaned audio is what is gated and saved; the recording then has the same 20 ms of delay as the sound you hear.

Troubleshooting

• Nothing is saved: the gate never opened. Lower the squelch, check the audio is audible, make sure the receiver is running.
• Many tiny files: with Split on, a noisy squelch opening and closing creates many files. Raise the squelch or the hang time.
• Words clipped at the start: the lead-in is short and fixed; use the mode's Hang to avoid cutting the end.
• Disk too slow: the log reports missing audio; record to a faster disk or use FLAC or MP3.

Related

Record audio and Monitor audio | Airband | General receiver | Legal