As a broadcast engineer, I have had opportunities to observe apparent
ground conductivity changes with temperature, and over at least some types of
soil, there does appear to be a fairly decent correlation (if not exactly
huge, under temperate conditions) at mediumwave.
The "Influence of Atmospheric Humidity on Low-Frequency Radio Ground
Waves" article, however, is one which caused a bit of a fuss when it first
appeared over here in The LOWDOWN. It invokes a new cause, without any
hypothesis for a working mechanism, for an effect that is already quite easy
to explain.
One might note that some of the numbers in the article have
pre-corrections applied that involve precisely the variables whose effects
are supposedly being demonstrated. Of course a "correlation" will be found
when one does that!
Furthermore, the atmospheric humidity values are not known over the
paths to the different stations whose signals are being measured...only near
the receiving site. It is not valid to assume the humidity is the same over
such a wide geographical area. (Nor is it legitimate to assume the radiated
power of each station remains constant, but that's another matter.)
If one disregards the pseudomathematical circular reasoning and looks
only at raw signal voltages, the only legitimate inference is that humidity
levels at the receiving site have an effect on the terminal voltage at the
receiving antenna--which is exactly what one would expect of an electrically
short vertical atop an unprotected insulator, feeding a high impedance
voltmeter.
In short, the data are meaningless.
For the experiment to prove the author's contentions, conditions over
the signal paths would need to be known to at least some extent, the field
strength would need to be measured with an environmentally protected active
whip antenna or loop antenna, the transmitter parameters or transmit antenna
current would need to be included, and the measured field intensities would
need to be presented without any sort of doctoring. In the years since the
article's first publication, this followup has not been forthcoming.
73,
John
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