[TowerTalk] I have a really stupid question (baluns and ununs)

[Keith Dutson]

What method other than coax is there to connect an unbalanced signal?  Does
this answer the question?

Keith NM5G 

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Rob Atkinson, K5UJ
Sent: Friday, November 12, 2004 11:40 AM
To: towertalk at contesting.com
Subject: [TowerTalk] I have a really stupid question (baluns and ununs)

Okay, I have what must be a stupid question.  I say that because I have
looked for an answer and have been unable to find one, so the answer must be
so obvious that I'm not seeing it and everyone else knows it.  Well, since I
have embarrassed myself before and surely will again and therefore don't
care about my reputation since I never had one anyway, I am going to ask
this question:

We commonly use ununs to transform one feed impedence to another, or
transform an unbalanced feed impedence to the feedpoint Z of an unbalanced
antenna.  The commercially available ununs have UHF females on each side of
them, which makes sense in the case of the 1:1 ununs and the ones that are
designed to transform 50 to 75 ohms which are common unbal. feed impedences.

I see a few ununs on the market that seem to be intended to work with very
low unbalanced impedences such as 5, 10 or 20 ohms, and they too all have
UHF females.  This does not make sense to me since as far as I know, there
are no 5, 10 or 20 ohm coax feed products out there that are commonly
available.  unless someone is working with some sort of complex arrangement
of 50 ohm feeds in parallel, these ununs are usually placed at the
feedpoints, as in for example a vertical that has a f.p. Z of 10 or 15 ohms,

right?   I'd appreciate it if someone would explain to me why a 50 to 20 ohm

unun has a UHF female on the 20 ohm side, since I don't know of any 20 ohm
coax, instead of a pair of lugs.  If at the feedpoint, do you simply defeat
the purpose of the UHF connector by clamping the counterpoise to the threads
and stick a short jumper to the vertical in the center?  There's something
wrong with this picture I'm missing.

tnx
rob/K5UJ

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