Tower talkers,
Have been following this thread with interest. The original question of
whether to reinstall the HyGain BN-86 voltage balun or to replace or even
supplement that balun with a current balun is an excellent question and gets
to the heart of the question of what elements contribute to a modern high
performance antenna system. The idea that "a balun is a balun is a
balun..............." is simply not consistent with contemporary engineering
knowledge and practice. Maximum antenna performance is only possible with
careful attention to the feedline / antenna transition.
Simply put, the purpose of a balun is to create conditions at the
antenna feedpoint such that the transmission line acts solely as a
transmission line (not an antenna in it's own right), and the antenna
performs as originally designed. Under certain conditions, a balun can be
dispensed with if careful attention is paid to the transmission line
installation. This approach is a highly specific for each installation, is
inherently narrow band and less than ideal for most triband and multiband
antenna installations.
The BN-86 voltage balun is a good example of the style of balun once
popular in amateur antenna installations. This style of balun is
characterized by limited common mode or choking impedance (a.k.a."balun
action"), a vulnerability to "saturation" of the ferrite core, and
relatively narrow bandwidth compared to the alternatives. When originally
popularized, this style of balun was a useful advance in antenna technology.
The modern ferrite core current balun is an adaptation of an alternative
style balun based on the principle of non-flux linked transmission line
transformers. These baluns offer a relatively high choking impedance,
relative immunity to "saturation" of the ferrite components, and extremely
wide bandwidths. They are simple to construct, rugged and weather resistant
if constructed carefully.
The BN-86 balun doesn't need to be replaced if it is in working order
and the owner is satisfied with the antenna performance. If the owner is
uncertain whether the balun is in working order, unsure whether the antenna
is handicapped by poor balun performance, or if he or she wants insurance
that what ever balun in use is offering the "latest and the greatest"
performance, by all means, replace with a current balun as described below.
Installing both a voltage and a current balun is probably not a good
approach because some of the inherent limitations of the voltage balun, i.e.
"saturation" potential, will remain.
I'm certainly interested in feedback from others if these ideas are way
off base or not.
Regards,
John Petrich, W7FU
----- Original Message -----
From: "Fred Hopengarten" <k1vr@juno.com>
To: <towertalk@contesting.com>
Sent: Wednesday, April 24, 2002 7:46 PM
Subject: Re: [Towertalk] Re HyGain Balun
> I have two HyGain TH6DXX and two HyGain TH7DX antennas in the air. I made
> up little plastic boxes from Radio Shack, mounted SO-239's and stainless
> steel studs (1/4-20 bolt and nuts) wired it to be the equivalent of
> splaying the coax (I was worried that it is hard to pevent water from
> getting into the coax and I preferred the ease of a PL-259/SO-239 when up
> in the air). Each coax has 6-7 toroid beads on the RG-213. Remember to
> put on the beads before the PL-259 (I own that T-shirt), or pay more for
> split beads (cheaper than re-doing the PL-259's, if you value your time).
>
>
> I have removed the BN-86's from service.
>
> Fred Hopengarten K1VR hopengarten@post.harvard.edu
> Six Willarch Road * Lincoln, MA 01773-5105
> 781/259-0088 *eFax 419/858-2421
>
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