[TowerTalk] Force 12 B-1/B-1S Baluns

[Jim Thomson]

Date: Wed, 15 May 2013 11:51:02 -0400 (EDT)
From: K7LXC at aol.com
To: towertalk at 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