[Top] [All Lists]

Re: [TowerTalk] Carolina Windom

To: Jim Jarvis <>
Subject: Re: [TowerTalk] Carolina Windom
From: Jim Lux <>
Date: Thu, 06 Sep 2007 08:59:49 -0700
List-post: <>
Jim Jarvis wrote:
> Guys...let me RESTATE my comments regarding the CW80,
> before we drag this thread through the fields of speculation:
> <snip>

Here's an interesting question.

Between a off center fed and a center fed dipole of the same length 
(e.g. something like the CW80s), and, assuming one has a reasonably low 
loss tuner to deal with the reactive component and match issues, what's 
the tradeoff between the two...

Seems like as far as radiation goes, the radiating part is the same 
(except for incidental radiation off the feedline, but the chokes 
theoretically prevent that), so, going off center just changes the range 
of impedances one has to match over the various bands.  As I recall, 
going off center makes all the impedances in the several hundred ohms 
magnitude range, so one uses a 4:1 or 9:1 transformer.

But, maybe the only real advantage is that it avoids some really 
obnoxious lengths to match (e.g. trying to feed a 40m center fed dipole 
on 20m leads to a VERY high impedance) by essentially moving the match 
to somewhere more convenient.

If this is the case, then one can also do a similar thing by just having 
a non-resonant length.. in the center fed case, make the dipole resonant 
at say, 8 MHz, so it's not an exact full wavelength on 14 MHz.  Then 
deal with the reactance at the tuner.

Jim, w6rmk

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>