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Re: [TowerTalk] Balun for Force 12 6 Element 20 Meter

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Balun for Force 12 6 Element 20 Meter
From: Grant Saviers <grants2@pacbell.net>
Date: Tue, 21 Jul 2020 16:31:17 -0700
List-post: <mailto:towertalk@contesting.com>
My strategy is no coax connectors out on a boom. Feedpoint ferrite chokes are in a PVC junction box with coax in thru a watertight gland and two glands out for short #10 leads to the feedpoint. So no exposed solder or connectors or nuts on plastic to loosen.

I've never figured out how to really make an S0239 watertight. It rains a bit here in Seattle.

Grant KZ1W

On 7/21/2020 15:17, jimlux wrote:
On 7/21/20 1:26 PM, Steve Maki wrote:
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.

I was thinking of the *wire* connections (e.g. to the driven element) where you'd have two studs that you'd hook a wire with a lug to.





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.

Yes..




-Steve K8LX

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