Not to mention the fact that the quarter-wave line is a quarter-wave
line at only one frequency!
----- Original Message -----
From: Dave D'Epagnier <[email protected]>
To: <[email protected]>; 'Pete Smith' <[email protected]>
Sent: Monday, October 18, 1999 10:11 AM
Subject: RE: [TowerTalk] properly feeding a tribander stack
>
> Pete, generally the reason why some people use odd number of quarter
> waves in feed line length is to reduce unwanted current from flowing
on
> the outside of an unbalanced transmission line (coax) when feeding a
> balance antenna (yagi, dipole). If the non antenna end of the feed
line
> has it's coax shield grounded, then the impedance of the line looking
> from the antenna back down the outside of the line will be high. This
> discourages current from flowing on the outside of the coax.
>
> A good balun will achieve the same result and can also work on more
than
> one band. I can't see any advantage to using quarter wave line if a
good
> balun is used.
>
>
> Dave
> K0QE
>
> ----------
> From: Pete Smith [SMTP:[email protected]]
> Sent: Saturday, October 16, 1999 8:18 PM
> To: [email protected]
> Subject: [TowerTalk] properly feeding a tribander stack
>
>
> I have been operating all along on the premise that in feeding a
> stack it
> is sufficient to have equal feedline lengths from a common
> feedpoint such
> as a stackmatch, in order to feed the driven elements in phase.
> Now a
> local has said that the feedlines should not only be equal in
> length but
> also an odd number of quarter waves in length. I vaguely recall
> a
> discussion of stacking several years ago on Towertalk in which
> one of the
> established experts said that it was necessary to do this to
> force equal
> currents in the driven elements, for the best possible pattern.
>
> Obviously, having to switch feedlines in order to meet this
> criterion would
> significantly complicate a typical tribander stack. Does anyone
> know:
>
> 1. Is this true, even in the abstract?
>
> 2. If it is, quantitatively, how significant is it?
>
> 73, Pete Smith N4ZR
> [email protected]
>
> Sometimes a tower is just a tower
>
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