[TowerTalk] need help identifying a vertical antenna...........

[Jim Brown]

On 8/23/2012 9:01 AM, rbig at cox.net wrote:
> 1.   I'm in a situation where I need to try to use a different kind of antenna.   I would like ot try a vertical, and see what changes it makes in my transmitting and receiving ability.
>
> I would like an antenna (commercial or homebuilt) which:
>
> *  Is somewhere around 30' in vertical length
>
> *  Base to be mounted 25' above ground level
>
> *  Uses few radials (4 or so)  <the radials will be insulated wire, and also be guys>
>
> *  does not need a base tuner (one in the shack is fine)
>
> Would greatly appreciate links to an antenna similar to this.

There's no magic to this -- antennas are conductors that are effective 
(or not) based on their length and shape. Length is ELECTRICAL length -- 
that is, as a fraction of a wavelength where you want to use them.

What you've described would work pretty well on 40M, not too badly on 
30M, and probably on 15M. It will be very difficult to load on 20 and 
10M, and while you can probably load it on 80, it won't work very well.  
The best link is to the chapter on antennas in the ARRL Handbook, and to 
the chapters on vertical antennas in the ARRL Antenna Book.

> 2.   We have a metal roof.   Is there any particular advantage mounting this centered on my roof?

Perhaps -- IF 1) all of the metal on the roof makes good electrical 
contact with itself, AND2)  if you can make good electrical contact with 
it at the antenna feedpoint.  #1 can be the tough one.

>    Or, are radials the trick?

Radials are a very important part of a vertical antenna.

73, Jim K9YC