[TowerTalk] short multiband dipole and 'isolation coils'

[Jim Brown]

On Sun, 14 Dec 2008 07:55:41 -0800 (PST), Gary Slagel wrote:

>Also, I'm planning on 2 antennas 90 degrees from each other.  
>Should I make sure and get a balun on the thing so that I get 
the
>uniform pattern I'm expecting?

The Hypower Antennas are good designs. I've had several of their 
longer ones in the air and like them a lot. They are a very good 
solution for limited space. 

See 

http://audiosystemsgroup.com/LimitedSpaceAntennasPPT.pdf

You should always use a good common mode choke at the feedpoint, 
but NOT a conventional "balun." 

See

http://audiosystemsgroup.com/RFI-Ham.pdf

Are you thinking of two antennas on the same feedline, or two 
dipoles, each on its own feedline?  You would need a transformer 
to put two on one feedline, and you would end up with a pattern 
that was approximately omni. If you have space, separate 
feedlines is much better -- you get 3 dB more gain from the 
directivity. 

73,

Jim Brown K9YC