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@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
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