[Hallicrafters] Re: Dipole antenna

[peter markavage]

Quote Glen - There have been amateurs who actually noticed a decrease in
performance by adding a balun.  But, in general, adding a balun will have
little, if any, effect on the performance.  There are exceptions, of
course, but I wouldn't go out and purchase a balun to put on a dipole
type of antenna.

You're right. Adding a balun will have little effect on performance of
the antenna. If you add one and performance decreases, it's either not a
1 to 1 balun or there's something wrong with it. However, the point of
using a 1 to 1 balun to interface between a coax (unbalanced) feedline
and a balanced antenna, generally helps performance between rig and
antenna. Connecting an unbalanced coax feed to a balanced antenna will
generally cause RF to flow down from one leg of the antenna down the
shield of the coax. This can cause unwanted radiation of the shield. This
can also affect your SWR as the coax moves in the wind and maybe comes in
close proximity to metallic objects. There are several ways to reduce or
eliminate this type of radiation besides a 1/1 balun including a 1/4 wave
stub of coax on the shield connected side of the antenna and even looping
several feet of coax feedline at the antenna input points. Not using a
balun is not the end of the world, and, as you noted, amateurs have been
going without them for years. However, having lived in residential areas
with typical 100 X 100 foot lots my entire amateur career, unintentional
feedline radiation that might cause interference to TV's telephones and
other electronic devices, is something I like to keep to a minimum. 

More info on this subject can be found in most of the ARRL Antenna Books
and other antenna reference material.

There ya go Hank, my pitch on antennas 101.

Pete, wa2cwa

On Tue, 22 Feb 2005 15:47:55 -0800 (PST) Glen Zook <gzook at yahoo.com>
writes:
> In theory, yes.  In a practical situation, probably
> not.  Amateurs have been feeding dipoles directly with
> coax for decades.  Sometimes adding a balun might help
> slightly in the pattern of the antenna.  However,
> there are so many objects near most dipoles that
> distort the pattern that in most cases you would have
> difficulty measuring the difference let alone noticing
> any difference in performance.
> 
> There have been amateurs who actually noticed a
> decrease in performance by adding a balun.  But, in
> general, adding a balun will have little, if any,
> effect on the performance.  There are exceptions, of
> course, but I wouldn't go out and purchase a balun to
> put on a dipole type of antenna.
> 
> Glen, K9STH
> 
> 
> --- Waldo Magnuson <magnuson at mac.com> wrote:
> 
> I have a question: My high (75 feet up)  40 meter
> dipole antenna is connected directly to  a coax (per
> ARRL handbook) instead of having a balun between the 
> antenna and coax.  I could build (or buy) a 1:1 balun
> but am I likely to see any difference?
> 
> =====
> Glen, K9STH