Re: LF: VLF grabber at DK7FC

[M0FMT <m0fmt@yahoo.co.uk>]

Congratulations Stefan

 

You are without doubt an inspiration to us all in the MF/LF/VLF field.

 

Many thanks for your efforts.
 

73 es GL Pete M0FMT IO91UX

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From: Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>
To: rsgb_lf_group@blacksheep.org
Sent: Fri, 15 April, 2011 20:25:46
Subject: LF: VLF grabber at DK7FC

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