Hello Alan,
Thanks for sharing your knowledge! Maybe i will have some questions to
you in some months when i want to come back to 137 with the 300m vertical...
I am not an expert in interpreting the propagation on VLF, it is rather
a daily study of my grabber pictures and watching out for unnormalities
of the daily QRN changes. It has been shown that there is a sector
between about 7...10 UTC where the overall noise is at its minimum.
Within, and mostly only within that sector it is possible to get a reals
distance on VLF. During the summer that sector changed, in its deepness
and broadness. There is a second QRN dip in the evening that is not so
deep and that wasn't visible in some days of strong QRN levels. In the
last days i observed that the average QRN levels decreased. I will watch
out for any changes and try to interprete them ;-)
Maybe it would be good to have a long time carrier on the dreamers band
to observe the daily changes of the S/N so that we can confirm what you
said is valid for LF!? That could be a relatively poor ERP since one can
choose long integration times. That cannot be done with a kite antenna
so lets wait for some further well eqiupped TX stns there. They will
come! :-)
TNX es 73, Stefan/DK7FC
Am 08.07.2010 00:27, schrieb Alan Melia:
Hi Stefan, be very careful about your belief that the noise is lower in the
morning !! This may not be the case. It may be quieter but..........There
are two components of noise local and distant It could be that the distant
noise is not propagaing as well at dawn!! This is what happens on 136kHz. It
was thought for a long time that this was the best time for QSOs.......but
in practice it was found not to be so. The best time was usually a few hours
earlier. Just pre-dawn at mid-path. The noise was higher but the wanted
signal was also a lot stronger.
I am cautious about extrapolating 136 to 9kHz but at 20kHz the morning an
evening dips on the stations monitored by SID detectors are due to increased
aborption. On 136 the mornings are quiet on the west coasts of Europe the
sun has destroyed the skywave from eastern Europe. On the Easten Coast of
the US the quietest time is the evening when the shadow is just aproaching
and the noise sources to the west are still in daylight. I admit I dont know
how the VLF noise behaves. Though I suspect a lot of that is lighning
induced.
Alan G3NYK
----- Original Message -----
From: "Stefan Schäfer"<[email protected]>
To:<[email protected]>
Sent: Wednesday, July 07, 2010 11:09 PM
Subject: VLF: QRN
Dear group,
Today the average VLF QRN level was pretty low! Also the minimum QRN gap
in the morning becomes braoder again. Maybe the most awaited DX period
starts slowly?
Best wishes, Stefan/DK7FC
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