[TowerTalk] Balun for Force 12 6 Element 20 Meter

[Steve Maki]

I've seen similar issues and no longer depend on the normal bolt and nut 
shield connection when there is a layer of PVC involved which is 
compressed by the bolt & nut. Any shrinking of the PVC will cause an 
intermittent connection. Most commercial baluns are still made this way.

Instead I replace one of the 4 machine screws with a solid #14 or #12 
wire that is soldered to the SO239 and sticks into the box 3/4" or 1", 
which the coax shield can then be soldered to.

-Steve K8LX

On 07/21/20 14:23 PM, dj7ww at t-online.de wrote:

> 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