Hello Jim, LF group,
Many thanks for your comments on my local noise report.
So one would expect predominantly "magnetic" noise from mains wiring. <<
That is what I thought as well. However, tests with a battery operated SPM-3
SLM, showed that local noise on an outdoor E-field antenna is substantial
less than on a magnetic field antenna.
I have also been testing this the other way round: reception of the carrier
of DCF-39 and semi-local NDB's. Mounting a mini-whip on a bamboo pole and
putting it outside an upstairs window, the signal of DCF-39 increases 22 dB.
Whilst holding a talk for the local ARC in a concrete buiding, the same test
was performed on 399.5 kHz. The difference was as high as 40 dB. One could
reason that the same attenuation level applies for propagation of indoor
electric fields to the outside world. So far my guess is that this explains
the low local noise level on my E-field antenna, though it is mounted only 5
metre from the house.
As we all know, magnetic field antennas, e.g. loops, do receive very well
indoors. Thus the same reasoning applies for propagation of local noise in
the magnetic field to the outside world: little if any attenuationa at all.
It should be nice if someone else could also perform these tests.
Best regards,
Roelof Bakker, pa0rdt
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