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[TowerTalk] balun beads for 9913

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Subject: [TowerTalk] balun beads for 9913
From: "Jim Thomson" <>
Date: Sun, 10 Oct 2010 05:26:29 -0700
List-post: <">>
For 50 MHz, you want two or three turns through a 1-inch long core and 
two turns through a 2-inch core,. and for maximum noise suppression, you 
will want at least three of these multi-turn chokes in series along the 
line, close to the feedpoint. The reason you need multiple chokes in 
series is that you only need 2-3 turns to put the resonance at 50 MHz, 
so you haven't got much benefit from N-squared.  Fair-Rite  #43 and #31 
are roughly equivalent at 50 MHz.

73, Jim K9YC

##  what do u mean by a 1" long core ?    Does this mean  2.4" OD x 1/2"  thick 
torroids used... and 2 of em stacked ?   Is a 2 " core  consist of 4 x torroids 

## It can't be ID.   You won't fit  9913 through a  1"  ID very easily..well 
maybe u can?
How  far apart is each of the 3 x chokes  to be spaced  from each other ?   How 
do u
propose to keep this mess away from the boom..and or mast ??   I think I would 
all of them to be at least one outer loop diam away from metal.     If they are 
metal, the C  between coax braid and boom/mast/tower  will surely screw up the 
chokes ? 
You would end up lowering their resonant freq.   The stray C would parallel 
resonate the
chokes..and probably increase the choking Z...  but at a lower freq.   It might 
be broad enough
peak to still cover 6m.  

## In some cases, you can't hang em below a boom...if the connections  are on 
top of the boom. 
Even if hung below a boom,  I would not want them flapping in the breeze.   
What's the fix ?  

Jim   VE7RF 


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