[BC] Short AM Tower

[Bobby Cox]

The low profile antenna (a.k.a. Kinstar) is a simple, series fed
configuration.  It's basically a really fat barrel formed by 4 vertical
cable elements that are then top loaded very heavily to give a fairly
uniform and high level of current in these four vertical elements.  The
4 top hat elements are much longer than you could put on a single stick
radiator via guy elements.  They extend out further than the barrel is
tall.

For a case when a single short stick is required, the best bandwidth
I've personally achieved is for a flared cage on a grounded mast.  We
use these for military all-band AM antennas.  We have to use a 50 meter
stick across the entire AM band.  An egg beater style cage can keep
reasonable bandwidth way down through the band better than any top
loaded, series fed configuration I've run across (on a single stick).
It stays reasonable on bandwidth on down to roughly 45 degrees height.
Below that it's tough going and the bandwidth narrows rapidly with
decreasing frequency. 

We use a slightly different version of the Kinstar on other military
fly-away broadcast systems that are much shorter than 50 meters.  They
use 4 poles and use the same concept as the Kinstar.....i.e. like a
series fed monocone.

Best Regards,
 
Bobby Cox , Ph.D.
Senior Staff Engineer
Kintronic Laboratories, Inc.
Phone:  423-878-3141
Fax: 423-878-4224
Email:  bcox at kintronic.com
 

-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net] On Behalf Of R A Meuser
Sent: Thursday, January 03, 2008 3:26 PM
To: Broadcasters' Mailing List
Subject: Re: [BC] Short AM Tower

About 30 feet of top loading and a fat tower (2 to 3 foot face) will get

the drive point impedance to a reasonable value. I would also agree with

those who suggest a series fed radiator. The simplicity will help keep 
the station with a good signal after the engineers leave. It would be 
worth getting this all properly modeled first to optimize the tower size

and loading.