There are other benefits besides pattern deterioration:
Without the balun, something like 1/3 of our power can head back down
the feedline shield as longitudinal current into our shack. This is
usually a great deal more than what is miscellaneously induced by
coupling from an antenna properly isolated from the feedline. This is a
common cause of RF in the shack and all the problems that causes.
Also without the balun, that feedline, which runs closer to our house,
and in miscellaneous directions can pick up all kinds of noise and feed
it to our antenna connection point (the balun is a TWO way block after
all) and thence coupled to the signal bearing system back to the
receiver. Especially if our feedline runs for any distance close to
power wiring.
In metropolitan areas, this last may be a huge advantage. How many times
have we just not been able to hear someone over all the man-made noise
on frequency?
After all that dough we just laid out for tower, rotator, antenna,
feedline, we're gonna skimp on a balun? Either we buy or make the
top-line balun, and put the proper finishing touch on that neat antenna
project we're just completing.
-----------------
Guy Olinger, K2AV
Apex, NC, USA
----- Original Message -----
From: John Petrich <petrich@u.washington.edu>
To: Sylvan Katz <jskatz@sk.sympatico.ca>; towertalk
<towertalk@contesting.com>
Sent: Saturday, January 20, 2001 7:20 PM
Subject: Re: [TowerTalk] RF Baluns (commercial or homemade?)
> Sylvan,
>
> Aside from the personal satisfaction that you may experience from
> building your own balun, you are more likely to do worse, making your
own
> balun, instead of purchasing one of these quality products. The
Force -12
> baluns are manufactured by Cal-AV and I consider them the same. I
have
> about #8 of these baluns in use on my antenna system and have
experienced no
> difficulties. The manufacturing specs, available from the Cal-AV
website,
> are impressive in terms of the common mode impedance, impedance
bandwidth
> and environmental protection. They employ the latest ferrite bead
balun
> technology to develop the needed common mode impedance.
>
> You didn't specify the type of Force -12 antenna that you have
installed
> and whether you have a single feed or multiple feed system. It is my
view
> that quality, high common mode impedance, broad band baluns are
necessary
> at EACH feed point to minimize common mode currents on all the
feedlines
> under all circumstances to avoid pattern deterioration. I think that
you
> will be very happy with either of the products that you were
considering.
>
> Regards,
> John Petrich, W7HQJ
>
>
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>
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