Hi all, We may be in for some improvements in night-time propagation now. We
have just had 3 straight days with the Geomagnetic Index, Kp<4, and the NOAA
SEC site forecasts quiet conditions for the outlook period. This would just
about bring us to the situation that, I believe, would give reasonable, if
not particularly spectacular, levels on the Trans-Atlantic path. My feeling
is that we need 7 to 10 days of quiet conditions during which conditions
will improve. This means that next weekend could be a fair window to try
before the summer noise conditions wipe out reception on the band.
The best guide will be to watch the site run by Steve Dove W3EEE
http://www.w3eee.com and click on the DCF39 Live tab on the left-hand side.
This will show a plot of the German utility station DCF39 for the last 24
hours. Good condition are long periods above -20dB peak levels are at
around -7dB for the best nights seen this year. One week ago the yellow
trace of DCF39 was within 1dB of the blue "noise" trace, but the levels have
been creeping up over the last few days.
Note though that the darkness path has shortened considerably since January.
The first rise in level is now not appearing until well after 2400z and dawn
in Europe determines the collapse of conditions. It is accurate enough to
consider the ground level dawn as the end of the night because the emerging
sunlight hits the ionosphere about 1000 to 1500 kms west of the ground level
dawn. It is this point that you require to return your signal for a two hop
path. The emerging sunlight lowers the "reflection level" and thumps in
about 20dB of attenuation, known as D-layer absorption.
Happy Hunting
Cheers de Alan G3NYK
[email protected]
|
