[TowerTalk] : Phased array radial query

[Dick Green]

>The radials
>cross each other at several points. What is the collected wisdom should I
>leave the radials insulated from each other or should I "bond" them at the
>cross over points?

I've got a full-sized 40M 4-square, with 60 radials per element, so lots of
wires meet in the middle of the square. Before building it, I tried to get a
definitive answer to this question and couldn't. I was never really clear
about it, but the argument in favor of bonding seems to have something to do
with currents from the radials of one element inducing small currents in the
radials of another element, upsetting the pattern. I think this may be much
more of an issue with a small number of elevated radials, which carry
considerably more current. More than one person told me that they had not
bonded the radials and that the 4-square performed to spec. Those who do not
bond tend to use insulated radials, but I'm not sure about the justification
for doing that.

Bonding was recommended by Colatchco, the original manufacturer of my
phasing box. Their successor, Comtek, recommends it, too. That's the primary
reason I decided to bond the radials. I figured as long as I was going to go
through a huge amount of work anyway, it would be worth it as insurance
against some real scientific reason to bond the radials. Also, it allowed me
to reduce the amount of wire required by a fairly significant amount, and
made the center of the square much neater. It was a lot of work to solder
and weatherproof each connection (to avoid corrosion of the joint.) But
because I had to pin my radials down every 6 feet due to uneven ground, lots
of work still would have been required to pin down the radials beyond the
crossing points had I not bonded. By the way, had I been forced by
availability to use insulated wire for radials, I would not have bonded them
(*way* too much extra work.)

>In looking at some older texts I notice It used to be popular to have a
>small ground rod at the far end of each radial. This practice seems to have
>vanished from vogue in recent years

Near as I can tell, the ground rod would add nothing. A friend of mine hotly
disputes the whole notion of an RF ground. His claim is that the earth is so
lossy that at the voltages we use, nothing much is going to flow into the
dirt. If it did, we wouldn't need the radials in the first place. The
voltages of lightning, on the other hand, are a different story. They seem
to be a lot more persuasive. Perhaps one of our experts would like to
dispute or agree with that theory.

73, Dick, WC1M



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