"Percy Picacity" wrote in message
...
Once you have tuned the radio (VFO) to get the wanted signal at the
centre of the crystal passband,

There is no passband, it is a single sharp peak.



you can set the BFO to taste and
altering the phasing of the crystal will not alter the IF frequency of
the wanted signal so won't alter the beat note.
If the phasing shifts
the crystal pass band significantly (which it probably won't) you might
need to retune the radio (VFO) slightly and then the beat note would
alter so you might have to adjust the BFO to taste again. But the BFO
won't alter where the signal is in the passband, and the crystal phasing
won't alter the beat note when it is adjusted. Only changing the VFO
could do that.

Sorry OM, but you're way off topic.

A single-Xtal series resonant XTal has a sharp peak, and then a deep null at
the parallel resonant frequency, and the phasing control adjusts the
position of the null.

My assumption, which is where I came in, is that the BFO would be centred
between
the two frequencies so that an interfering signal at the audio image
frequency would
be nullified.