> Uwe, back again this afternoon?
Some signals on the band would be handy.
Trying to test new E-field rx against old with the two
planted side by side on a bleak moorland hillside.
Needed some weak signal so made up a little near field tx
starting with 280V to a 'long' wire, 3m long 1m high.
150m away from the rx with a small plantation of trees in
between but the signal was way too strong. Ended up with
a few volts from a sound card onto the wire.
New rx design models well and it tests pretty good on the
bench, but when deployed performs poorly. Noise floor is
consistently 1.4dB higher on the new rx than the old, and
the old one is quite noisy anyway. I've no idea where the
noise is coming from. Thermal noise of ground resistance?
No, the new rx has a better ground.
It's a black art, this stuff. A VLF rx is just an audio
amplifier, how hard can that be?
The antenna too is fighting back. Despite sealing with
O-rings, flexible sealant, and layers of self amalgamating
tape, it still manages to fill with water after a few
days of rain.
When I eventually get this thing running and calibrated,
the spectrogram at
http://abelian.org/vlf/fbins.shtml
will gain a dB or two sensitivity and be steerable
modulo 360 degrees instead of 180.
--
Paul Nicholson
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