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Opt-in channel-power squelch for AM audio RX (#3315)

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* AM: add opt-in channel-power squelch for AM audio RX

Add an SDR++-style power squelch on the complex channel signal for the
Analog Audio RX app in AM modes (DSB/SSB/CW). The squelch measures the
mean channel power, converts it to dBFS, and mutes the demodulated audio
when the signal is below a user-set threshold. Being carrier-based it
keys on the AM carrier (e.g. airband/ATC) rather than on audio-band
noise, which the existing FM squelch could not do for AM.

A new 'SQ' field (0-99, 0 = off) is added to the AM options view and is
persisted per app via app_settings. Default is 0, so existing AM
behaviour is unchanged unless the user enables it. Threshold maps 1..99
to -80..-20 dBFS.

Touches: message (AMConfigureMessage.squelch_level), baseband_api
(AMConfig::apply), receiver_model (am_squelch_level get/set),
app_settings (persistence), proc_am_audio (DSP), analog_audio_app (UI).

* Refactor audio power calculation to use magnitude squared

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
This commit is contained in:
Mo
2026-09-14 20:54:54 +02:00
committed by GitHub
parent d72b5ed0b1
commit b8ad44c431
11 changed files with 78 additions and 10 deletions
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firmware/common/message.hpp
+5 -2
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@@ -739,7 +739,8 @@ class AMConfigureMessage : public Message {
const fir_taps_complex<64> channel_filter,
const Modulation modulation,
const iir_biquad_config_t audio_hpf_lpf_config,
const size_t channel_spectrum_decimation_factor)
const size_t channel_spectrum_decimation_factor,
const uint8_t squelch_level = 0)
: Message{ID::AMConfigure},
decim_0_filter(decim_0_filter),
@@ -748,7 +749,8 @@ class AMConfigureMessage : public Message {
channel_filter(channel_filter),
modulation{modulation},
audio_hpf_lpf_config(audio_hpf_lpf_config),
channel_spectrum_decimation_factor(channel_spectrum_decimation_factor) {
channel_spectrum_decimation_factor(channel_spectrum_decimation_factor),
squelch_level(squelch_level) {
}
const fir_taps_real<24> decim_0_filter;
@@ -758,6 +760,7 @@ class AMConfigureMessage : public Message {
const Modulation modulation;
const iir_biquad_config_t audio_hpf_lpf_config;
const size_t channel_spectrum_decimation_factor;
const uint8_t squelch_level; // AM channel-power squelch threshold (0 = off)
};
// TODO: Put this somewhere else, or at least the implementation part.