[Hallicrafters] Dipole antenna balun question

[Charlie]

Well, it may not be any better, but it would in fact be different.  By
connecting the (unbalanced) coax directly to the (balanced) dipole, some
radiation will occur from the shield of the coax which, when combined with
the radiation from the antenna itself will cause the pattern, or
directionality of the antenna to shift  from what it would be if either a
balanced feed or a Balun were used.  The balanced feed, or use of a Balun,
will effectively eliminate that coax shield radiation so that the pattern of
the dipole will be more like the textbook donut  around the antenna.  No
practically installed dipole will actually have that perfect donut radiation
pattern, but allowing the shield radiation will make it change a lot more
than it would be if a balanced feed were used.

Another big advantage of balanced feed twin lead, is that it has much lower
loss than coax under high SWR conditions.  So, if you're planning to use the
antenna on many bands with a tuner, by all means, go for the twin-lead, or
heavier ladder line.

However, if you're only going to use the dipole only at resonance and you're
happy with the performance, it probably wouldn't be worth the trouble to use
twin-lead or install a Balun.

73' Charlie k3ICH

----- Original Message ----- 
From: "Waldo Magnuson" <magnuson at mac.com>
To: <hallicrafters at mailman.qth.net>
Cc: "Waldo Magnuson" <magnuson at mac.com>
Sent: Friday, January 16, 2009 11:20 PM
Subject: [Hallicrafters] Dipole antenna balun question


> My 40 meter half-wave dipole simply feeds a co-ax cable (RG-8X) where
> the center conductor is connected to one side of the antenna and the
> shield to the other side.  It seems to work pretty good and the SWR is
> near one.  My question is:  Would a balun between the antenna and the
> co-ax perform significantly better?  Or using a twin-lead show any
> difference? Or even using a folded dipole and 300 ohm line or a 3-wire
> folded dipole and a 600 ohm line be worth the effort?  Or just go on
> the air more often with what I have?  Thanks in advance for your
> thoughts.
> 73,  Skip  W7WGM
> P.S.  I've been able to talk with CO, ID, CA, HI in the last few weeks
> with my dipole and HT-44 at 80 watts.
>
> ______________________________________________________________