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Re: [TowerTalk] Feedline (choke) question

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Feedline (choke) question
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Thu, 2 Oct 2025 20:05:49 -0700
List-post: <mailto:towertalk@contesting.com>
On 10/2/2025 10:47 AM, Steve Harrison wrote:
I have also heard of big multi-multis experiencing connector generation of spurious products due to poor or loose coaxial connectors, which can result from thermal expansion/contraction. Dissimilar-material coaxial connectors can also cause problems; I remember reading of one in New England that took the station operator SEVERAL YEARS before he accidentally ran across (and cured) the real source of the spurious products that had plagued his operators for years.

I also have served for more than 30 years on the AES Standards Committee WG on connectors. We've dealt entirely with those used for pro audio. For decades, the only players in the world of analog audio have been Switchcraft, based in Chicago, and Neutrik based in Liechtenstein. Since digital audio started taking over, we addressed connectors for those systems.

Sometime in the '90s, engineers representing these companies began reporting issues with production tolerances in counterfeits. It's entirely possible that this could be a contributor to the overheating you're describing.

DIN connectors in the family that were widely used for control circuitry in ham gear were widely used 60 years ago in Europe for pro microphones. They were a high quality product. Switchcraft sold them in the US, and I but I think they were made in Europe. Pro audio in Europe eventually switched to the XL-connectors for mic and line level that I believe were developed in the US, by Cannon. Switchcraft came along as a competitor, and Cannon gradually disappeared.

Twenty years ago, I wanted to stock up on males in that DIN series for radios I was using, but all I could find was junk from Asia. They had dissimilar metals, metals that wouldn't take solder, and a dielectric that melted when you tried to solder to it.

73, Jim K9YC

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