Actually you could make the inner tube as long as you want
and it won't make any difference as there is nothing to excite
the capacitor formed by the concentric tubes. The end where
this coaxial capacitor connects to the antenna (i.e. the swaged
element joint) is shorted out. You would have to insulate the
inner element from the outer element at the swaged joint in
order to excite the capacitor. In that case, the amount of
overlap will dictate the amount of coupling to the element tip
and have a significant effect on tuning.
73 de Mike, W4EF........................................................
----- Original Message -----
From: "Don Havlicek" <n8de@thepoint.net>
To: "Dino Darling" <k6rix@arrl.net>
Cc: <towertalk@contesting.com>
Sent: Thursday, December 05, 2002 7:21 PM
Subject: Re: [Towertalk] Dumb Question (swagged elements)
> Dino,
> I've used those same element segments to build MANY antennas over the
years.
> the simple answer is NO .. it won't affect the electrical length as the
> 'capacitor' isn't long enough to be a significant portion of a
> wavelength on the band of interest, and it won't have sufficient
> 'capacity' to make a difference.
> Good luck
> Don
> N8DE
>
>
> You wrote:
> I have a couple of old Hy-Gain antennas with swagged elements. I get
> these for free when I take down old towers.
>
> Lets say, for argument, that we have two elements. One slides inside
> the other, which is swagged in order to meet the outside diameter of the
> first one.
>
> These two elements can be tuned to different frequencies by adjusting
> the length the first element slides INSIDE the other. To exaggerate,
> lets say the first element is 12" inside the swagged element, but the
> only contact area between the two elements is the few inches where the
> second element is swagged. The rest of the first element is hanging out
> "in free space" (for lack of a better term).
>
> Here is the question...will the element INSIDE the other affect the
> electrical length of the entire assemble due to the extra metal in "free
> space"? Although it is a direct short, will there be any capacitance
> much like a gamma match where one material is suspended inside the other?
>
> Dino...k6rix@arrl.net
>
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