The fldigi port ran a fixed 600 Hz NCO, so any real signal not inside
600±75 Hz (the 150 Hz filter passband) decoded nothing — the decode rate
was effectively zero unless the tone happened to be on frequency. This
mirrors the behaviour of the removed channelTracker: a sliding spectral
peak detector now steers the NCO to the strongest tone.
Changes:
- Collect raw input, run a 512-pt Hann-windowed FFT every frame, find
the strongest bin in 300..1500 Hz (CW range), smooth-track it.
- First strong peak locks immediately (no RX reset, so the triggering
element survives); later large jumps (>120 Hz) retune and reset the
fldigi state machine; small drifts are eased at 20%.
- Absolute energy floor (peak < 30) so silence/noise never steers.
- estimatedPitch now reflects the tracked tone frequency.
Verification:
- New unit test: 900 Hz "CQ" with decoder initialized at 600 Hz decodes
correctly and pitch moves to ~900 Hz.
- All 9 decoder tests pass; full domain/cw/radar test suites green.
mckero
09ebf1f39a