Dear group,
Today, my VLF grabber at
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html
becomes 1 year old :-)
I've never thought that it will be so sensible and will see so many
stations, even with usual LF home antennas and moderate power. The
circuit of the active antenna was modified several times. Also Spectrum
Lab by DL4YHF plays a dominant role here. By improving the noise
reduction settings, we won another 2 dB (about).
First it was a idea of Paul Nicholson to choose a compromise of a long
(enough) "carrier" and sending informations. So i came to the good old
"DFCW-600". Since my signal was strong out of 40km distance i wanted to
add a DFCW-60 and DFCW-3 window, to monitor my own signal in faster
modes. For test purposes i arranged a DFCW-6000 window. The idea was
that someone who prepares to be visible in 600 could see his signal in
6000 and then knowns how many dBs are still missed. OE5ODL for example
showed often that he is visible in 6000 but just sometimes, with the
balloon, in 600.
Now we arrived at even 60000 (= 47 uHz). Stations like DJ8WX became
regularly visible. But there seems to be a limit, given by the VFO
accuracy, time and phase instabilities at higher distances.
The Alpha stations are a perfect reference and since having a stable RX
is essential and there were often questions about the availability of
RSDN-20, i added the Alpha window, not only to check if my GPS module is
still locked.
The wideband window gives a good overview of the current QRN situation,
solar activities and the presence or absence of military MSK stations or
fauls of the rig, that shows in a sudden loss of sensitivity.
Thank you for the interest of 7314 visitors out of 60 countries (34 of
51 US states) and 198665 pageviews so far :-) I'll keep the service
running as long as possible, and this may be a looong time!
Stations who appeared there so far were: DF6NM, OE5ODL, OE3GHB, DJ8WX,
OK2BVG, DK7FC and a small sign of PA3CPM
I hope to see more stations soon!
73, Stefan/DK7FC
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