[TowerTalk] tower mounted vertical

[paul@w8aef.com]

And please don't forget that elevated radials will be resonant.  Gotta be 
cut to your desired operating frequency or they will really upset the tuning 
of the vertical.  I would expect that at least a pair of radials for each 
band will work.

de Paul, W8AEF

----- Original Message ----- 
From: "Terry Conboy" <n6ry at arrl.net>
To: "Tim Kass" <timkass at hotmail.com>; <hcawthra at sbcglobal.net>; 
<TowerTalk at contesting.com>
Sent: Sunday, June 12, 2005 1:20 AM
Subject: Re: [TowerTalk] tower mounted vertical


> At 05:03 PM 2005-06-11, Tim Kass wrote:
>>If you slope the radials, that will lower the impedance a bit, for a full
>>size 1/4 wave ground plane it will match 50 ohms...either way it shouldnt
>>change more than about 20 ohms and should still present a decent match to 
>>50
>>ohm coax.
>
> I'm sure Tim meant to say that the impedance will go up with sloped
> radials.  I modeled quarter-wavelength verticals on a 50 foot tower, with
> four 45 degree sloping radials.  The feed impedance at resonance varied
> between 33 and 50 ohms, not bad.  (Many people don't realize that a ground
> plane with four horizontal radials in free space is about 22 ohms instead
> of the 36 ohms plus ground losses seen with the radials on the dirt.)  Of
> course, with a trap antenna, things will likely be somewhat different.