Uh...because that's the way I've always done it??? ;-)
The twist is there for the same reason flat TV lead used to be twisted.
Disturbances caused by proximity to other objects is supposed to effect both
conductors equally so that the system stays balanced. Another alleged
benefit is that signal pickup, on receive, is cancelled by inducing equal
and opposite currents. This is supposed to reduce noise pickup by the
feedline. I'm not sure this really matters in amateur practice where the
load and line are not the same impedance. And for what its worth, I couldn't
find any quick references on this question but I'm assuming it goes back to
the same reasons 600 ohm audio or telephone cable was twisted as is cat5
cable etc.
A side benefit with commercial ladderline, my opinion, is the line doesn't
have a large continuos flat surface to catch the wind so it doesn't flutter
as much. I was more concerned with the line flexing and eventually breaking
than with electrical balance.
Pat, WA4TUK
> -----Original Message-----
> From: Paul Christensen [mailto:paulc@mediaone.net]
> Sent: Friday, March 31, 2000 3:44 PM
> To: Patrick A. Thompson Sr.; tentec@contesting.com
> Subject: Re: [TenTec] Re: Ten Tec antenna tuners
>
>
> >the tuner to the window feedthru plug. Beyond the window feedthru is 14ga
> >ladderline with a slow twist.
>
> What benefit is derived from twisting the feedline? Is it physical or
> electrical? From the 1920s and '30s issues of QST, I often find
> descriptions for adding "transposition blocks" on the feedline every few
> feet. This, in effect, forms a twist on the line as well, except that the
> twist is the reverse from the prior twist or transposition. If
> transpositioning the feeder was so popular then, why don't we see the
> technique discussed and used today when using balanced line?
>
> -Paul, W9AC
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