In the past year, I have made and measured (on a network analyzer) seven
choke baluns, made of multiple turns (5 to 7) of RG-142 through multiple
cores (3 to 5, 2.4" OD) of type 31 material, all depending on the
application: 2 each for 20, 15 and 10 YO-designed monobanders and one TH-3
tribander. These are packaged inside 3" PVC pipe, with internal spacers to
keep the turns separated as much as possible. The finished unit is
typically 5" to 6" long.
I had the same concerns about boom proximity effects - so I measured them.
I wanted to use a hose clamp to attach the round balun parallel to the 2"
round boom that I was using. I measured choking Z of the balun(s) by itself
and clamped to a chunk of 2" boom material on the bench. I measured no
significant degradation of swept Z. There were slight changes in the
performance - some freqs better, some worse - but the changes were in the
hundred Ohms range in chokes that were measuring in the thousands of Ohms.
I concluded that I was not degrading the performance of my antennas by
using the construction and mounting technique described.
73,
geo - n4ua
On Wed, May 15, 2013 at 11:51 AM, <K7LXC@aol.com> wrote:
> >Not only that, but taping the choke to the boom is adding extra
> capacitance between one side of the driven element and the boom. In other
> words,
> taping the "choke balun" directly to the boom is making the antenna more
> UNbalanced! It's amazing to watch people doing this...
>
> So what else are you supposed to do with it? It obviously isn't a
> fatal problem.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
>
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