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
Sent: Friday, December 12, 2014 9:24 AM
Subject: Re: VLF: 8819.9 Hz in Virginia?
Spectrogram covering 24 hours yesterday
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).