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Binaural without carrier lock

Posted: Mon Dec 21, 2020 11:46 am
by pauldbnut
Mentioned before, but thought this ought to be a new request.

The carrier-locked mode gives excellent results bringing a channel-dominant station into focus. At the same time, a co-channel weaker station tends to be masked. Experiments without carrier lock suggest that a continuously-tuned mode can help separate stations with small carrier offsets.

This is not a "magic wand":
  • It does not somehow "magnify" a weaker station
  • It cannot somehow separate two stations with the same offset
  • Without a lock, you will still get slow fading/wandering
But "near-lock" does help the brain focus on one rather than another. In practice:
  • Steps at least as fine as 1 Hz are needed (I found 0.1 Hz much better)
  • A maximum offset range of about +/- 50 Hz covers most MW offsets
  • Some kind of tuning indicator would be an enormous help
That last is something I could never get right because of my hopeless DSP ignorance.
The best I ever managed was a 2-channel "scope" showing tuned frequency waveform, and received carrier after an extremely narrow filter, speed and direction of phase shift being the tuning cue. It was rubbish, not least because I can'r design filters!