Squelch improvement
Continuously calculate noise floor and lower threshold level if less noise was received. High noise or ongoing transmission during start of program will not cause a threshold that is too far above the actual noise floor.
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@ -44,9 +44,9 @@
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*/
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/* NOTE: SQUELCH must be calibrated !AFTER! DC bias, to get the actual noise floor */
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#define SQUELCH_INIT_TIME 1.1 /* wait some time before performing squelch */
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#define SQUELCH_AUTO_TIME 1.0 /* duration of squelch quelch calibration */
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#define SQUELCH_AUTO_OFFSET 6.0 /* auto calibration: offset above noise floor */
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#define SQUELCH_INIT_TIME 0.1 /* wait some time before performing squelch */
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#define SQUELCH_AUTO_TIME 0.5 /* duration of squelch quelch calibration */
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#define SQUELCH_AUTO_OFFSET 10.0 /* auto calibration: offset above noise floor */
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void squelch_init(squelch_t *squelch, int chan, double threshold_db, double mute_time, double loss_time)
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{
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@ -89,12 +89,19 @@ enum squelch_result squelch(squelch_t *squelch, double rf_level_db, double durat
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squelch->auto_count += duration;
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squelch->auto_level_sum += rf_level_db;
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squelch->auto_level_count++;
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if (squelch->auto_count < SQUELCH_AUTO_TIME)
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return SQUELCH_MUTE;
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squelch->threshold_db = squelch->auto_level_sum / (double) squelch->auto_level_count;
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PDEBUG_CHAN(DDSP, DEBUG_INFO, "RF signal measurement: %.1f dB noise floor, using threshold of %.1f dB\n", squelch->threshold_db, squelch->threshold_db + SQUELCH_AUTO_OFFSET);
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squelch->threshold_db += SQUELCH_AUTO_OFFSET;
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squelch->auto_state = 0;
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if (squelch->auto_count >= SQUELCH_AUTO_TIME) {
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double noise_db, threshold_db;
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noise_db = squelch->auto_level_sum / (double) squelch->auto_level_count;
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threshold_db = noise_db + SQUELCH_AUTO_OFFSET;
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/* must be 0.1 dB smaller, so we prevent repeated debugging message with similar value */
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if (threshold_db < squelch->threshold_db - 0.1) {
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squelch->threshold_db = threshold_db;
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PDEBUG_CHAN(DDSP, DEBUG_INFO, "RF signal measurement: %.1f dB noise floor, using squelch threshold of %.1f dB\n", noise_db, threshold_db);
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}
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squelch->auto_count = 0.0;
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squelch->auto_level_count = 0;
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squelch->auto_level_sum = 0.0;
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}
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}
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/* enough RF level, so we unmute when mute_count reched 0 */
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