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Re: [TowerTalk] dipole length adjustment

To: "Dan Zimmerman N3OX" <>,
Subject: Re: [TowerTalk] dipole length adjustment
From: Jim Lux <>
Date: Mon, 22 Jan 2007 12:05:48 -0800
List-post: <>
At 11:33 AM 1/22/2007, Dan Zimmerman N3OX wrote:
>Jim Lux suggests:
> >For instance, you could take the existing tuner Bud is using, put it
> >in a weather proof enclosure, add some servos or steppers, etc.  But
> >that's probably more of a pain than just running the openwire line.
>I dunno, that's what I did.  Granted, I had a balcony with a roof to
>limit the amout of weatherproofing that I had to do, but the servo
>thing was cheap and fairly reliable, even though it was a pretty ugly
>hack the first time.  In my case, I had to run all feedlines out under
>the balcony door so ladderline wasn't an option.  (And yes, I had
>noticeable feedline loss on some bands with coax, even with a 20' run

There's a lot of ways to do it.  I've used approaches like simple DC 
gear motors and a video camera looking at the faceplate for 
feedback.  Pretty low buck and simple approach, but does not lend 
itself to automation.  Synchros are another possibility, if you can 
find a cheap surplus source for the devices.

If there were sufficient demand, I suspect that someone would make 
high power matching networks designed for feedpoint use as a product.

Heck, come up with a rational and reasonable set of requirements and 
I might do it.  Things like what impedances need to be matched, 
what's the maximum loss you're willing to accept, and how fast the 
matching needs to be changed.  It's not going to be cheap, 
though.  The SGC 235 is rated at 500W PEP (200W CW) is $1300 and the 
Palstar AT-AUTO1500 is $1200.  Neither of these is particularly small 
and lightweight, but, then, nothing that handles high power AND is 
weatherproof is.

Jim, W6RMK 


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