Date: Wed, 15 May 2013 11:51:02 -0400 (EDT)
From: K7LXC@aol.com
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Force 12 B-1/B-1S Baluns
>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
## Obviously the answer is to not use a solenoid wound choke, made from coax.
They don’t work anyway.... so why mess with em. Z is way too low, and you
will
unbalance the yagi if its near the boom. It would have to be at least one half
it’s diam away from the
boom or metal. 4 turns of 393 Teflon coax wrapped around
4-8 type 31/43 2.4 inch od torroids, and stuffed into a nema box works
great.
The coax back to the tower can be taped or ty rapped to the boom.
## two foot worth of type 31 beads slid over 213 or 393 coax also works good.
## If a remote switch box is used at the top of a tower, I install a 2nd
choke on the
INPUT side of the remote switch box. Typ another nema box, with 4 turns of 393
around 4-8 torroids..then a 3rd box mounted on the SPG in the basement.
Anything that
gets past the yagi feedpoint balun, gets killed by the 2nd choke at the input
of the remote switch
box. problem solved.
## The torroids are typ rapped, and the mess hangs dead center inside the nema
box. Then
box is bolted to a flat plate, then onto mast or tower or boom etc. Silver
solder everything,
and use 7-16 Din connectors...and it will never blow up. Put some silica gel
inside the gasketed nema
box, and u won’t get moisture inside it either.
## Coax braid is bonded to top of tower via the remote switch box. It’s also
bonded to base of tower
via the hoffi lightning arrestor. The lightning arrestor also makes for a good
demarcation test point. It’s
also used to interface the larger rigid coax from shack to base of tower.... to
the slightly smaller coax
going up the tower. Coax braid also bonded to SPG in basement wall.
## It’s 2013. The days of solenoid wound, coiled up coax for a choke are
long long. That’s
arrl fubar techniques.
## the real test is to use a clamp on rf ammeter, a real one, and run it up
and down the coax.
## m2 has no clue how to build a balun, and neither does cush craft...and a
bunch of others.
later... Jim VE7RF
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