Lou,
I find that viewing the output on an audio spectrum analyzer (I use
Spectrogram) helps, one can see the beat to a lower frequency that
normal hearing. Just watch the amplitude of the signal - when the beat
goes to as close to zero as you desire, you are "there". I have found
that I can easily get as close as 1 beat in 5 seconds, which is 1/5 Hz
or .2 Hz in the final calibration.
There is a limit to the DAC steps that may keep you from getting to an
absolute zero beat - this is not an analog thing, but then it is more
stable than an analog VFO, so there is some tradeoff.
73,
Don W3FPR
On 5/19/2021 6:54 PM, Louandzip via Elecraft wrote:
I count beats. One beat in 1 second and I'm off 1 Hz. One beat in two seconds
and I'm off 1/2 Hz. Easiest done if the side tone and received signal are
adjusted to be close in amplitude and there's little/no QSB. Zero beats, and
the frequencies would be exactly the same, but the practical limitation is
probably 1/4Hz in good conditions. The only things required are a reference,
like WWV, and my ear.
That is, after all, what the term zero beating means, adjust frequencies to be
the same until the beats stop.
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