I
am out of range (Arizona this weekend) for your experiment,
but interested. I have carefully measured infrastructure
effects (including buried utilities and other utilities),
and have coincidentally seen roughly 6km range (at VLF
frequencies) in a scenario that is somewhat similar. For
what it’s worth I found steep field gradients near 3km-6km
(infrastructure and topology dependent) in four directions,
and did not have time or RX dynamic range to determine
whether these gradients were associated with multi-modal
interference nulls, utility decouplers, or simply extinction
of the reactive field. I hope to extend my RX dynamic range
by ~ 20dB in the near future, and will repeat these
measurements (at ranges > 6km) at that time.
Does
your infrastructure broaden your signal and/or add spurs? I
suppose you can’t know this until your test is underway, but
it might be helpful for others to eventually know this, on
the chance that some infrastructure resonating off center
frequency has a large aperture and could therefore be
detected more easily than the fundamental at ranges >
6km*.
At
50V, 1.5A (~ 33 ohms) do you think that you are losing any
current to undesired paths?
Best
of luck on your tests.
73,
Jim AA5BW
*
(given your antenna contact separation, it seemed that
infrastructure aperture might be significant compared to
coupling between your earth loop and the infrastructure, for
RX separations > 6km, at which distance the reactive
field may be giving way to aperture-dependent quasi-static
and radiative field components)
G3MFW has problems posting to the Groups at
the moment, I have received the following from him.
I have been
experimenting with earth systems for some years. I now use the
house water pipes and an array of 11 copper earth rods and
buried sheet in parallel, 30 metres away at the bottom of the
garden. At 8.9758 (crystal) I pass 1.5 amps at 50 volts RMS. I
have made a reception map around Truro, Cornwall, at 1.46Hz
bandwidth using a 41 turn horizontal loop on the car roof
rack, supplemented by using the same loop on the ground.
Ranges vary greatly with topography and earth conditions, but
are up to 6 Km with buried utilities assistance.
I will
transmit this Saturday, 21st Dec, from 9.00 to
10.15 am using QRSS 3 with endless dashes. I would be most
grateful if you would report any reception using narrow
bandwidths. I must be exciting several square kilometres of
buried utilities – surely SOMETHING must be radiated! I can
repeat the test at any time upon request.
Harry
Woodhouse, G3MFW
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