[Antennas] Mosley Classic 33 Balun?

Sat Dec 11 15:54:09 EST 2004

Don Boyer wrote:
> I recently obtained a Mosley Classic 33 antenna that appears to be in
> excellent shape. It has an SO-239 coax connector to the antenna's
"Classic
> Match". The Mosley website indicates that for The Classic System: "To
> isolate the outer coax conductor from ground, the coax line is coiled for
a
> few turns near the antenna end. This is designed to prevent the very
> unlikely effect of Feed Line Radiation". I have also heard that with the
> Classic 33, you can connect your coax directly to the SO-239.
>> Is this coiled coax actually needed and if so, how many turns, what
diameter
> is the coil and where is the coil located? (I typically use RG-8 coax)
Any
> comments regarding this interface would be greatly appreciated. The
coiled
> coax may not even be required. This is unclear to me.
>> Also, any repair / maintenance pointers would be helpful before I put the
> antenna on my tower. Thank you.
>> Don - WB0AIN
>
Hi Don, any coax-choke employed will always be right at the base of the
antenna, just prior to the antenna connector. This in not very practical
with RG-8 as it would require very large diameter turns (3 or 4 turns are
fine for any choke). If you think its important, then do so. But a balanced
antenna is not going to cause feedline radiation to any degree that matters.
Should you drive it well outside its intended bandwidth, that's another
matter. Shield-grounding the coax to the tower ground at point of antenna
attachment and at ground level of the tower, and at entrance to the station
are critical for lightning protection if you are in an area subject to
lightning. This also serves to decouple feedline radiation on the outer
shield of course.
Best regards,
Jack Painter
Virginia Beach Virginia