LF: 8.76kHz earth mode tests today

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Today being mild and dry (and less muddy) for the first time in almost 6 weeks, I decided
 to do a field test with my improved 8-9kHz tuned preamp and loop 
antenna. A 5W QRSS3 "earth mode" (through the ground) test signal was 
emitted using my 20m spaced earth electrode pair on 8.760kHz from the 
Burwell QTH. I ventured out into the countryside armed with the 80cm 
loop and preamp to see where the signal could be copied. In addition to 
my usual test sites at 1.6 and 5.1km I tried other directions and sites 
today. A map showing where signals were/were not received is attached together with a screen shot taken at 4.75km west of the TX.

The signal does seem to travel along the METAL water pipes, which must 
be absent to the east of the QTH beyond the village, where I assume they
 must be plastic, at least in places. No reception away from roadsides was attempted. Reception is definitely not as good at 8.76kHz as it was at 0.838kHz but
 this could be because the ground was saturated with rain from the last 
few days, or perhaps because sections of pipes have been mended with 
plastic pipes since last summer.

Ideally I'd like to repeat the tests in dry weather on 8.76kHz and on 
frequencies around 6, 4, 2 and 1 kHz (avoiding mains harmonics) to see 
how signal levels compare. Last summer the earth mode signal at >5km was so 
strong in places on 0.838kHz that 10wpm CW was copyable by ear. Signal levels must be around 10dB weaker at 8.76kHz than on 0.838kHz. 

These tests are not in the same class as the radiated DX being achieved by several stations now, but I know some on this list are interested in these rather less earth-shattering experiments. Also, it is the sort of experiment that anyone can undertake without great expense or effort. I question whether an NoV is strictly needed considering the signal radiated must be in the pW region.

73s
Roger G3XBM


-- 
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G3XBM   GQRP 1678    ISWL G11088

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