[TowerTalk] Baluns, BN-86 et al

jim henderson jhenders@tdrss.wsc.nasa.gov
Thu, 20 Feb 1997 01:47:20 +0000

        Mark, my experiences with the BN-6 now lead me to discard it when I
open the antenna box. Someone with the measurement gear and math skills can
explain why it should work, but I think they just fail too often, with less
than 1200W out, and with the antenna Zi near where it should be.

        Other similar problems with other companies' baluns caused me to but
Jerry Sevick's book on the subject. You can roll your own quite easily with
that book. I also bought one of the 4:1 baluns made from his data and sold
by Amidon Associates (I think!), and use it with my big LPDA. It appears
much more robust, and I assume the same would hold true for the one you need. 

        Somewhere I lost the notes I made from taking apart the balun from
an old Telrex TB5EM. This was nothing more than some large coax (RG-213?)and
a #12 insulated wire wound into a very few turns and placed inside a
weatherproof box. There was no ferrite to fry. It gave every indication of
being a good balun and having the long life of a simple, successful design.
Just the sort of thing you want for your topmost, "hard -to-reach" antenna. 

        I never made measurements of this design, but perhaps one of our
esteemed reflectee colleagues did, or knows how to reconstruct one. 

73 de Jim, KF7E

Jim Henderson

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