If one has (or has access to) a synthesized signal generator, that can
be set to the exact desired BFO frequencies with less than 1 Hz
resolution AND accuracy, then there is no reason one could not listen to
the beat between that signal generator and the BFO one is aligning to
get +/- 1 Hz accuracy. It does not matter that the audio stages of a
receiver don't pass sub Hertz audio frequencies, because you can hear
sub Hertz modulation of noise. Any AM receiver that can be tuned to the
BFO frequency can hear the beat between the BFO and the signal generator
you are using as a reference. Getting the amplitudes of the reference
signal generator and the BFO adjusted to be able to hear the beat may be
a bit tricky.
Using that same method to adjust the 10 MHz reference oscillator you can
also get it adjusted to within less than one Hertz of your reference
signal generator.
If you are so unlucky as to have both errors adding (the cumulative
error of your two adjustments) instead of cancelling, the whole system
would still be within only a couple of Hertz of correct.
Sure, that is more effort than just looking at the readout of a
frequency counter, but it is a valid and accurate method of
accomplishing the task. Whatever method you use is completely dependent
on the accuracy of your reference, be it the time base in a frequency
counter or the time base in your synthesized signal generator.
DE N6KB
I've said it before and been criticized but one needs a counter to resolve the
required frequencies to 1Hz or better. Confirming SSB USB & LSB frequency
requires measurement, not listening.
Bob, K4TAX
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