Hi Roger,
First, congrats to the 3 km in QRSS-3! This allows you to do local QSOs
:-) What about G6ALB? Has he tried to receive your transmissions as
well? This would allow you both to to a QRSS-3 VLF QSO!! Have you tried
this?
Am 03.02.2011 11:35, schrieb Roger Lapthorn:
What I do NOT understand is why I get ZERO signal pick-up from G6ALB at
3km with another earth-electrode set-up at the RX end. One of my ground
points is the copper central heating radiator which connects directly
to metal pipes in the road. I know this as I use the same set-up to
launch my own earth-mode signals that can be detected in the roads with
a loop out in the fens >5km away.
...but in your own experiments you received your signal with the loop
and here you want to receive it with the earth electrodes. This seems
to show that it is easier possible to receive the magnetic field caused
by the current flow in the pipes than measuring a current flow through
the soil between your electrodes in your garden (causing a potential
difference between them).
Logic tells me that if Andrew G6ALB is launching his
signal along pipes from his earth electrode pair then I would get
strongest signals by also connecting one ground to the metal pipework
at the RX end, but this is definitely not the case as there is
absolutely no signal detectable in QRSS3 by this method, but at least
20dB S/N with the EFP! Can someone explain what is going on please as I
am very baffled!
Check if there is a difference in the signal level and SNR if you
disconnect the EFP from the local ground, i.e. use a battery and a
notebook. Go out in the fields with all 3 forms of antennas (loop, EFP,
earth electrodes) to check the difference at an equal distance. If the
noise and a reference signal (e.g. Alphas) stays at the same level but
your 9 kHz signal level is strongly reduced, it may have been supported
by the quasi galvanic coupling to one of the TX antennas legs. This may
be the difference compared to your own transmission. As you've been /p
with your RX, there was no ground connection to the TX!
Go out in the forest, far away from pipes and cables and install a
large (real) earth antenna, pointing to G6ALB. First you may try to
receive G6ALB with the EFP and/or the loop.
Good luck and fun with your experiments!
73,Stefan/DK7FC
PS: Which of the 3 antennas gives you the best SNR of the Alphas? Which
one shows the sferics as the dominant noise source arround 9 kHz? :-)
What about mains hum? Will you try to receive me this weekend? :-) Most
probably i'll do the 10th this sunday!
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