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Thanks Dex for sharing this extremely
interesting observation. My first thought was that the ripple might
have been a beat pattern caused by an interfering carrier at 1/20 Hz
offset. But this explanation doesn't hold, because the periodicity would
have been broken up by HGA carrier spreading due to the FSK telegrams. So
it has to be some propagational effect.
On SXV, on rare occasions I had observed
a slant color ripple pattern, i e periodic variation in the apparent
direction of arrival:
I had attributed this to an unusually late
and Doppler shifted ionospheric component. There may possibly a connection
to aurora, and perhaps the recent period of solar activity. However nothing unusual was seen here on LF last
night.
Best 73,
Markus (DF6NM)
Sent: Friday, February 18, 2011 3:45 AM
Subject: LF: HGA22 plot
This evening I was watching HGA22 with SpecLab plotter.
When I first
started the plot I noticed the signal looked as expected but
when I
increased the speed I saw a sine wave shape on the plot. After
watching
it for a while the sine wave pattern changed to a normal
pattern. I
wish I had made more captures of the signal but I only made
one which
shows the change.
http://www.w4dex.com/lf/HGA22_plot_18feb11.jpg
FWIW
if anything,
Dex
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