On Aug 25, 2005, at 9:32 PM, ersmar@comcast.net wrote:
> You might have heard/read that thick shunt wires provide better
> match/greater bandwidth/increased stamina, etc. Just hang two or
> more of the thinner wires off some kind of insulating support (PVC
> or wood come to mind) off the tower and tie the top and bottom ends
> together to form a shunt wire with a larger effective diameter.
You don't need an insulator for this.
I have a 44 foot tower, and I used a 3 foot piece of 1" angle
aluminum with a couple of U-bolts around the tower legs. This places
the end a good foot and a half off the tower. A 1 foot piece of 3/4"
angle aluminum spreads the two wires. There's no insulation at the
top. At the bottom, I have a 5" NEMA box. The wires join to another
piece of 3/4" angle aluminum, which are held with a single #10
stainless bolt through the NEMA box. The box contains the matching
networks for 80m and 160m.
The wires hang free, side by side over about 42 feet. Works well. I
tried the shunt originally with one wire just six inches off the
tower - very much harder to match.
> OOT (one other thing): Keep your shunt wire(s) an appreciable
> distance away from the tower face. My wires (I use two in
> parallel) are two feet off the Trylon tower face; I've seen others
> as much as five feet away. I'm sure modeling will tell you why
> this is preferred; I just followed others' examples.
I think the big reason is that it is easier to match a skeletal
ribbon a couple of feet off the tower.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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