Dear Roger,
this is interesting! I wonder if you attempted to estimate ERP or antenna
efficiency. A measurement of effective height (ie. volts per fieldstrength
for RX, or sqrt (EMRP) per current for TX) could be used to calculate loop
area and "effective depth" of the return current. You could also compare
540+ kHz or 198 kHz BC signal voltages with reference to a small nonresonant
loop.
Best 73,
Markus (DF6NM)
From: Roger Lapthorn
Sent: Wednesday, June 16, 2010 9:10 PM
To: [email protected]
Subject: LF: Who needs antennas! - success with ground electrodes on 500kHz
Well, I'm amazed.
This evening I connected my 500kHz transverter straight to the two
connections of my sub-9kHz grounded electrodes and TXed WSPR. No attempt was
made to match anything on the assumption that the two electrodes system
looked not too far from 50 ohms resistive as measured between 1-9kHz.. Pout
from the IRF510 is around 5W. What happened?
Three people copied me - M0BMU, G7NKS and M0JXM with reports between -21
and -28dB S/N. The wire to the furtherest ground rod is at most 20m long and
most of the way it is 1.5m above ground. Once again, this must be acting as
a pretty effective loop mostly within the ground. Screen grab of the WSPR
log attached.
So, if you live on clunchy chalk soils like me then don't worry too much
about big antennas, :-)
73s
Roger G3XBM
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