[Elecraft] Frequency Accuracy and stability

[Don Wilhelm]

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.
>