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Hmm 8820 Hz is a 60 Hz multiple, so maybe
not the best choice for American observers. On the other hand, the
trace at Forest seems to be too stable for a direct mains harmonic.
What I often see here both at VLF and LF are
crystal controlled carriers, accompannied by sidelines at 16.7 or 50 Hz
multiples, presumably from railway power converters which are driven by a
microcontroller.
Best 73,
Markus
Sent: Friday, December 12, 2014 9:24 AM
Subject: Re: VLF: 8819.9 Hz in Virginia?
Spectrogram covering 24 hours yesterday
http://abelian.org/vlf/tmp/141211c.gif
A
wandering signal from a crystal source of average stability.
These are fairly
common when you dig deep enough into the noise.
Fortunately easy to
distinguish from a GPS locked amateur signal.
Demonstrates how useless an
undisciplined xtal osc is for VLF
(tx and rx).
--
Paul
Nicholson
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