[TowerTalk] Balun for Force 12 6 Element 20 Meter

[dj7ww at t-online.de]

Before WX0B switched to use feed through insulators I replaced two of his
baluns on Optibeams at a friend.
Baluns were made from RG393 wound through ferrite toroids.
Around the stainless steel screws the boxes were burnt out, I guess that was
caused by current, not by voltage and went into a loose connection and
thermal runaway.

I also use feed through insulators, either ceramic from my junkbox or home
brew teflon.

New insulators can be found here:

https://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx

73
Peter

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Jim
Thomson


<I don?t think so, he is not even using feed through insulators.

<73
<Peter

##  speaking of feed through insulators,  who makes em, that have a .25-20
or
.25-28  brass thread  through the middle ??   Looked  everywhere, and cant
find any. 
Or is a  feed through insulator  even required on a nema plastic /
fiberglass box ?  
A  divider wall  glued or rtved into place, midway  between the 2 threaded
lugs should suffice  to increase V breakdown  from
water, rain, debris, gunk  build up.  I dont see any   feed through
insulators used on  steve,  ve6wz,  nema boxes,  but the outputs
are well spaced apart.

##  I have  tried making hb  feed through insulators using 1 inch  solid
teflon  rod, with a .25  hole down
the middle of each rod...done in drill press.   This is on the outside of a
nema box.  .25-20 brass threaded  rod was then silver plated,
and inserted through each hb insulator,  with a  1 inch diameter rubber
gasket, between nema box and bottom of teflon rod. 
2 x more hb insulators, but a lot shorter, used on inside of box.  I found 3
inch long, solid brass,  .25-20 bolts  locally,  plus mating
brass nuts, washers  etc. 

##  works, but nothing sticks to teflon  for water proofing.  I have not
tried white delrin rod,  it might succumb to UV. 
I was just trying to use what I had available  around the shop. 

Jim  VE7RF

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