In rec.radio.amateur.antenna, W8JI writes:
On Mon, 23 Aug 1999 12:00:31 GMT, [email protected] (Tom W8JI)
wrote:
In the latest installations and rebuilds, VLF stations have removed
multiple downlead systems and improved efficiency. I'm sure I can did
some references.
OK Nate. Unlike you, I'll be helpful and post a clear reference that
does not reference myself and includes an A-B comparison at one site
with only a grounding system change .
19-14 of the Antenna Engineering Handbook by Jasik.
A 26 KHz VLF antenna at Marion, Mass in the USA used a mutiple tuned
system. The average dry/wet efficiency was 15.6 percent, with ground
resistance averaging .32 ohms but with variations up to .615 ohms in
dry weather.
The Air Force rehabilitated the system with a conventional radial
system occupying the same overall area. Average efficiency became 23
percent.
An exact quote:
"With the same antenna, site, and expanse of ground system and at the
same very low frequency, a generally radial ground system resulted in
considerably less ground loss than had previously been obtained with a
combination of multiple stars, parallel wire grids, and a complex
overhead distribution and equalizing system."
IMO, with a ham doing things "less perfect" than commercial ventures
and on a much higher frequency than 20 KHz, he would be well advised
to avoid all the complex theories about multiple distributed grounds.
Especially since they don't work as well as a simple, straightforward
system of radial wires occupying the same physical area.
I'm sure this carries over to HF as well, at least my results and the
results at two AM BC stations and reports from others using both
"special" and conventional systems compared at one site all
agree...the conventional system is better.
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