On Mon, 17 Jan 2011, Markus Vester wrote:
Between 12 and 18 UT today, again Ossi's fieldstrength has gradually
decreased on Stefan's grabber in Heidelberg (about 400 km), while it has
increased for Lubos, Gerhard's and myself (all ~ 200 km). It looks like
it may have been increasing also for Jacek (~ 700 km) but I'm not quite
sure about the time scale of his screenshot.
attached is another screenshot, with the timescale visible. the time is in
UTC+1. you can just see the trace around 14:40 UTC, then it gets stronger,
then the QRM gets stronger, then at around 17:20 UTC the signal is covered
by the noise.
regarding OE3HGB tests from january 15 - Gerhard turned off the tx around
14:40 UTC for a while, after that i couldn't receive anything.
This seems to confirm that a) VLF interference fringes are fairly
reproducible from one day to another, and b) they vary with range in a
non monotonuous way, but do not depend on direction or absolute
positions.
probably the high interference times coincide with long distance
propagation, bringing in more atmospheric noise. so the best period for me
is just before that, when the path is good for 700km (in case of OE5ODL),
but still not good enough for much larger distances. probbaly there is an
explanation using some eartg-ionosphere waveguide model and changing
ionosphere height during the day.
VY 73
Jacek / SQ5BPF
oe5odl_t.jpg
Description: JPEG image
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