I use 36 foot booms with insulated elements for my 10 meter 6 element stacks.
36 foot booms degrade the performance of 20 meter antennas within 500 feet, and
the degradation is serious within 200 feet.
My detuning approach is both direct (requires no adjustment) and effective. My
36 foot booms are sectioned into three 12 foot pieces, coupled with Type LE
phenolic tubing.
73
Frank
W3LPL
---- Original message ----
>Date: Mon, 30 Nov 2009 13:06:39 -0800
>From: Michael Dinkelman <mwdink@clearwire.net>
>Subject: [TowerTalk] Electrically lengthening a boom
>To: Towertalk <towertalk@contesting.com>
>
>I have a 40M beam underneath a tribander with about 8 feet of
>separation. The tribander is on the mast and
>the 40M beam is on a Tic Ring so both can be rotated independently. All
>is well as long as both booms are aligned.
>Once the the two start getting a few degrees (~30) out of alignment,
>the SWR on 20M starts rising until I get to
>90 degrees (3.3:1) then starts going down again until I reach 180
>degrees. Yes, the boom of the 40M beam is
>darn close to resonant on 20M as it's about 32 feet long. (15M and 10M
>are unaffected) I've put up with this
>for a couple years because I really don't want to bring that 40M monster
>(to me) down.
>
>So, I was investigating detuning the boom (all the elements are isolated
>from it) when I came up with another
>possible idea for electrically lengthening it. Why can't I...
>
>1) drill a small hole in the boom
>2) insert some stiff wire (or even tubing) inside the boom and push it
>through until it comes out one end
>3) electrically connect the wire to the boom where it goes through the hole.
>
>Wouldn't that make my boom longer as far as the 20M elements of the
>tribander
>are concerned? I wouldn't think I would have to go too far out the end
>of the boom.
>Even if the wire hangs down a bit off the end that shouldn't be an issue.
>
>Suggestions?
>
>cheers
>dink, n7wa
>
>
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|