[email protected] wrote:
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
This makes sense and all the recent theory/mathematical supposition about the
subject is a nonsense, especially about measuring TX power output at the remote
RX site. The recent observations from G3LDO about watching out because YOUR
POWER
output can be calculated, is totally misleading. Is he concerned that someone
might gain an advantage by running an extra few m/watts. Each and every radio
station operational, especially on LF has a totally different set of
circumstances, not least local environment, coastal, inland, flat and wet,
mountainous etc, local temperature variations, path to rx station.
Why are so many concerned about this aspect instead of getting up a good high
resonant antenna, a good radial /ground system and fire up and get some
practical
results. All the theory/mathematics and papers about the subject have been
written over the past 80 years and just need browsing if one needs information.
Why re- invent the wheel?
It is obvious on the 136 khz band who has the best signals, those with HB
purpose
built transmitters, and those who put some effort into antennas, and radial
systems.
de G3KEV
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