Hi ULF,
Since a few hours i'm running 15 mA antenna current on 970 Hz, the 309
km band. This requires to apply 5 kV to the antenna. You can see a very
faint trace on the lower image at
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
Just about 10 dB SNR in 424 uHz in 3.5 km distance, or in 0.011 lambda
distance. The receive antenna is a H field antenna that is not even
pointing to the transmitter. Also the preamp noise is dominating the
background noise on that frequency. So the RX is deaf on that band.
Anyway, there is something.
The ALC into SpecLab does a very good job, it holds the antenna current
stable during all the changes and working point drifts. The plot can be
seen at http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png
15 mA results in an ERP of 3 nW.
My new preamp circuit is waiting for a first test together with the
large loop. I hope to pick up the signal in at least 5 km distance with
that preamp which is really low noise down to the lower Hz range.
An E field reeiver would be a better choise for the reception from that
E field Tx antenna, at least in the lower near field. Maybe that will
give another test then.
With 30 kV i could reach 0.3 uW. Not sure where this could be detected?
And who knows the advantages of this part of the spectrum for our
purposes!?!
Since 21:20 UTC, a 2 character EbNaut message is running. It will take
2h, 2min, 40s. Hopefully the tree grabber is available until the message
ends. It will shut down in a few hours due to lack of solar energy in
these days (an improvement of this system has already been prepared and
waits for the installation).
73, Stefan
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