"GW" wrote
I have a question similar to but different from the one posted a few lines
below. How do you determine the quality of an antenna ground at HF on an
absolute basis? Not how well have I maximized what Mother Nature gave me
at
my QTH by adding radials, but how good is my ground compared to other
stations' grounds at other locations? I have read about the advantages of
seawater, ground conductivity etc as guidelines, but how is overall ground
quality (not just soil resistivity) determined objectively if indeed that
is
possible at all?

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The performance of a ground electrode system cannot be separated from that
of an associated antenna. But at least the antenna can be standardised by
assuming it to be a simple vertical of given height. And we won't go far
wrong by assuming the antenna efficiency to be 100 percent.

Engineering Quality is a numerical measure of how well something serves its
intended purpose.

Since the purpose of a ground + antenna system is to radiate em waves the
only possible numerical measure of Quality is radiating power efficiency
measured as a percentage.

With beautiful and fortunate simplicity, the radiating efficiency of such a
system is given by -

Eff = Rrad / ( Rrad + Rloss ) times 100%.

where Rrad is the antenna's radiation resistance looking into the base of
the antenna, and Rloss is the resistance looking into the focal point of the
ground electrode system, immediately under the antenna, such as a set of
radial wires. Or it may be a single rod.

It is impossible to separately measure Rrad and Rloss. But Rrad can be
calculated from the antenna's height and diameter and the two can be
measured together. From the combined single measurement the efficiency can
easily be calculated.

And that's where we part company with simplicity.

To calculate your "Quality on an absolute basis" of just the single ground
rod involves a list of numerical variables as long as your arm. To calculate
Quality of a system of radials imposes an impossible, intractible problem in
statistics.

To compare one system with another would involve everybody with several
lifetimes of fundamental research, measurement and guesswork which would get
nobody anywhere.

However, because radio is by far the most inexact of all the engineering
sciences, it doesn't matter a toss. All measurements are subject to error.
In most of which even the standard deviations can only be guessed at. When
will the next flare occur on our unstable Sun?

Radio engineers are quite accustomed to allowing safety margins of plus or
minus 15 or 20 dB along propagation paths. Even then distortion and error
rates are quoted. Brute force and ignorance and a lot of luck prevail.

So it doesn't matter whether or not Rloss lies between 1 and 10 ohms when
used with your top-band inverted-L and you havn't the foggiest idea what the
soil resistivity is in YOUR back yard.

Incidentally, ground loss is not only smaller in sea water, it is also
smaller with soil resistivities of several thousand ohms and greater.
There's a maximum somewhere in between.

To crudely estimate ground loss, download program RADIALS2 from website
below. It's all crammed into only 70 kilo-bytes. Nobody has yet complained
it gives the wrong answers.
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Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
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