[TowerTalk] Balun for Force 12 6 Element 20 Meter

[Steve Maki]

On 07/21/20 15:49 PM, jimlux wrote:

>> 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.

> Or 4 nuts - nut1 wire nut2 pvc nut3 wire nut4
> The preload between nut1 and nut2  and the preload between nut3 and nut4 
> are what make the contact. Takes two wrenches to get it tight enough.

I thought of that, but then you have a nut between the SO239 flange and 
the box. It starts getting messy. BTW just so we're on the same page - 
the connector flange is on the outside of the box, which is almost where 
it has to be for ease of assembly.

>> 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.

> That works fine for a coax connector, although now you've got a 
> "non-disconnectable" connection.

The center conductor is soldered to the center pin, and the braid is 
soldered to the *ground pin*. What's not dis-connectable?

> Actually, a banana jack/plug would probably work. They're spring loaded, 
> so they don't have thermal cycling issues.

I realize now the OP was talking about the antenna/binding post side of 
the box. I haven't had a problem on that side, probably because there is 
a large flat washer on either side of the PVC.

-Steve K8LX