Topband: "Linear Loading" & 160-Meters

[Lars Harlin]

----- Original Message ----- 
From: "Wayne Rogers" <n1wr at chesapeake.net>
To: <topband at contesting.com>
Sent: Friday, February 26, 2010 1:07 PM
Subject: Re: Topband: "Linear Loading" & 160-Meters


> While we're on the subject of Bobtails - I've been considering a design 
> that
> is slightly different than what you normally see.
>
> What if one were to use a cylindrical tube for the center element, and run
> the coax up the cylinder to the top and connect to the current feed point
> there?  This solves the problem of how to run the cable for a current 
> feed.
> Would any ground plane be needed?  How would you connect it?  Would this
> work?
>
> This for an application on 40 or 80 meters - too long a center element for
> 160.
>
> Thanks, Wayne N1WR
>

Interesting thought Wayne!
It might work, but guess you would have use a RF choke on the coax at the 
bottom of the element. On the negative side is that it would be at a hi-z 
point of the coax where the choke will be less effective. There will be a 
severe capacitive coupling between the coax and the feeder. If it works no 
ground plane would be needed.

Myself I use a corner fed half square on Topband, using coax and current 
balun. In my opinion it works great!

73 de Lars/SM3BDZ