Alan,
What do you think about the remaining signal of DCF39 after the sunset?
Is it really DCF39? Or a local QRM line? I once took a recording and
reprocessed it here on my PC. I saw there is a local line (without the
data bursts) but it was some Hz below DCF. Since the receive system is
reasonable stable (drift < 0.1 Hz) i reduced the frequency range for
detecting the signal level for the DCF plot to a BW of 1 Hz. Anyway
there appears a trace which is > -30 dB below the night peak but anyway
visible. Realistic? That path is almost completely over water. In some
days you can even see the steps of S/N reduction due to the sunrise in
the reflection zones. At least it looks like that..
With a receive loop in winther i think even G3KEV has a chance to appear
there ;-) For winther i expect at least a 10 dB S/N improvement, maybe
rather 20 dB. A loop which cancels the noise from the southern
hemisphere, many stations will have good chances to appear in SA i think.
73, Stefan
Am 22.06.2012 01:46, schrieb Alan Melia:
Hi Stefan, this is a function of propagation, I think. It depends on
where the interference originates. Because there is virtually no
skywave propagation in the "sunrise dip", no noise is propagated by
skywave (> 1000km) from the east. Where you live you have large cities
all round you. We get this effect on the edge of Europe as the
daylight kills the night-time propgation of noise fron the East (there
a few big cities or industrial noise sources for 3000 km W of Ireland
:-)) )
It was thought at first that this would be the best time for DX, but
despite trying it didnt work out that way. Mike G3XDV and Brian CT1DRP
tried quite hard..... but eventually made the qso mid morning, when
the noise was up again due to increases in daytime skywave!! That is
if I remember correctly.....it fascinated me as I was just getting
interested in LF long distance propagation around then. We found
evening effects in Nova Scotia and I believe similar effects were
reported by John W1TAG and Jay W1VD who are very close to the US East
Coast.
Alan
G3NYK
----- Original Message ----- From: "Stefan Schäfer"
<[email protected]>
To: <[email protected]>; "YV7MAE Maritn A. Echazarreta D."
<[email protected]>
Sent: Thursday, June 21, 2012 11:22 PM
Subject: LF: 15 dB noise drop in 20 minutes
Hello Martin, LF,
I'm fascinated by the noise drop on LF which occurs during your
sunrise. On your grabber
(http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html ), i can
see the noise drops 15 dB within 20 minutes. That means the sun must
be very strong so the ionosphere is very quickly ionized. Also the
local lightning density must be extreme. All in all it looks like a
very sensitive system. But some directivity would be interesting :-)
73, Stefan/DK7FC
PS: I will be on 136.172 kHz again this night, starting in a few
minutes...
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