Dear Roger,
just one suggestion: perhaps you could soften the display contrast a bit, to
allow better visibility during the daytime periods when QRN is low.
The strange 8970.1 signature is very narrow so certainly of human origin,
and probably crystal controlled. Could be some timer-activated device in the
neighbourhood.
Best 73,
Markus (DF6NM)
From: Roger Lapthorn
Sent: Wednesday, March 09, 2011 5:20 PM
To: [email protected] ; Stefan Schäfer
Subject: Re: LF: VLF dj8wx on 8970.022Hz
Hi Stefan,
I enclose here the full wider band 3 day plot of the noise (and mystery
signal) as received in 424uHz BW here in JO02dg near Cambridge. Do you have
any comments please? The mystery signal appears on all three nights at
8.9701kHz. It looks like a little "hook" shape over about 4 hours.
BTW, the loop/preamp system is receiving the alpha beacons very well,
typically 20dB over the noise. See
http://www.youtube.com/watch?v=TDxRhQYg7lQ for a video showing alpha beacon
reception using the SM6LKM software VLF receiver.
If the interference/noise at 8.9701kHz was natural then surely it would be
amazing for such signals to exactly repeat 3 nights running at exactly the
same frequency? OK, I agree the general background noise floor may be partly
man made and partly the natural noise floor changing diurnally but the
oddity at 8.9701kHz?
The grabber is currently OFF as I shall be away for a couple of days, but
still in email contact.
73s
Roger G3XBM
2011/3/9 Stefan Schäfer <[email protected]>
Hello Roger,
Am 08.03.2011 20:51, schrieb Roger Lapthorn:
Nothing visible on my grabber https://dl.dropbox.com/u/15047843/xbm_grab.jpg
yet this evening but I have a high noise level in the evening hours from
lights, TVs etc.Leave the TX running overnight please as I hope to see your
signal after midnight and through tomorrow morning. In the 423uHz bandwidth
and with the slow scroll speed it will be more difficult to see than when
you were sending a continuous carrier a few days ago.
Are you sure it is local QRM? Maybe its just the usual QRN that risies
strongly in the evening. It is as strong as never before within this year
now :-( And things will get even worse. We have to make QRO, faster than
nature does it ;-)
To check the local QRN/QRM situation it would be helpful (and interesting!)
to have a wideband screen from you. If you want, you could run a second SL
instance simultaneously and upload the pictures. You know how the wideband
windows looks, from grabbers like TF3HZ which is most interesting each day
:-)
Also you may arrange a real website and store it on your dropbox. There you
can include several pictures in one link, the link to the website :-)
Best 73, Stefan/DK7FC
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