[Elecraft] Spectrogram and frequency markers

Sun Aug 24 16:36:01 2003

Since the subject of frequency calibration has moved from practical, to
theoretical, to philosophical, to obsessive, I offer one more suggestion for
those of us who just can't leave well enough alone.  The Spectrogram
approach that looks at the 500 and 600 Hz. markers is great.  But the
question still remains, how accurate is the Spectrogram program?
Spectrogram allow you to set the frequency resolution, so that's easy.  What
we don't know is how accurate is the soundcard A/D conversion timing?  This
will, of course, affect the frequency binning of the audio signals analyzed
by Spectrogram.  One way to account for this timing is to tune in the AM
broadcast of WWV with an AM receiver, and see where the 500 and 600 Hz audio
tones fall on the Spectrogram display.  Those frequencies are the ones you
want to match in USB and LSB modes.  You will find that they may be off by
several Hz from what Spectrogram thinks is 500 and 600 Hz.

Now, back to thinking about the effect of Doppler shift on the frequency of
the
received tones caused by the Earth's rotation ...

Have fun!

Rich W1EZ

----- Original Message ----- 
From: "belsley" <[email protected]>
To: <[email protected]>
Sent: Sunday, August 24, 2003 11:10
Subject: [Elecraft] Spectrogram and frequency markers

> I note a number of people suggesting the use of Spectrogram's frequency
> markers as means of determining, say, 500 or 600 Hz.  Just how precise
> are these markers in Spectrogram?  Do they not depend on some
> frequency standard in the computer, and as such, are they not themselves
> subject to error and change somewhat from computer to computer?  What
> sort of precision is to be expected?
>
> thanks,
>
> dave belsley, w1euy
>
>
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