At 07:15 PM 5/30/98 -0500, Chuck Sudds wrote:
>At 09:45 AM 5/30/98 -0700, Kurt wrote:
>>A tower in concrete, connected to a ground system, has lower inductance
>>than any of the other paths on the tower. Continuous grounded guys make it
>>better for the lightning but not so good for the antenna patterns.
>Just *how* badly does continuously grounded guys mess up the antenna
>patterns on 20-15-10 meters?? I seem to recall an article in QST or some
>other publication about 10 years back that stated that most installations
>will suffer only marginal degradation... on the order of 1/4 db or so. Did I
>misread this or have there been more recent studies?
The article was by K4VX, and while I don't doubt his antenna smarts, I
think it would be a stretch to conclude anything from that one situation.
I'm using continuous guys for my 100' Rohn 25, except that the top 21' of
the top guys is a Joslyn fiberglass power pole insulator. My guys are
grounded at the anchor end. The lower 2 sets of guys are insulated from
the tower right at the tower, so that I can shunt feed it on 160m. later on.
Modeling of my complete station shows essentially no induced currents in
the guy wires from the Yagi (10-40 meters) on top. Not surprising
considering the relative angles and the 21-foot isolators. However, I will
clearly have to replace my top guys with something else when I model a
stack with a second tri-band yagi underneath, because the effect on the
pattern of those wires in the near field is disastrous. Also, I use an
80-meter parasitic array hung from the tower, whose elements run parallel
to the guy wires and not that far away. Modeled, there is a LOT of current
in the tower and the guy wires, but by dumb luck the current seem to
contribute to performance.
The bottom line is .... model it and see.
73, Pete Smith N4ZR
In wild, wonderful, fairly rare WEST Virginia
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