[TowerTalk] Wireman W2DU Current Type Balun

Tue Dec 27 04:50:10 EST 2022

Hi Rich,

You can get a commercial choke showing in excess of 5K Ohm at 28 Mhz, up to 3Kw:

https://myantennas.com/wp/product/cmc-130-3k/

If you prefer to build it yourself, you just need to follow Jim´s Cookbook:

http://k9yc.com/2018Cookbook.pdf

73,

Máximo EA1DDO

www.EA1DDO.es

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Richard Smith
Sent: martes, 27 de diciembre de 2022 0:53
To: towertalk at contesting.com; Jim Brown <jim at audiosystemsgroup.com>
Subject: Re: [TowerTalk] Wireman W2DU Current Type Balun

I can see that my initial request included far too few details. Thanks for the many good responses.

The responses were very helpful for me. I'll try to refine my request.

1) Approximately 5000 ohms choking resistance at 10 Meters.2) A design that can easily handle 1500 Watts into a 2.5:1 max SWR load.

In preparation for my next contest effort, I already have about 30 tasks on my Task List. I was hoping that a suitable commercially made choke balun would be available so that I would not have to design and build them. From the responses to my initial request, it looks like no one on TowerTalk can share any first-hand experience with the Wireman W2DU choke balun. Also, the Balun Designs 1115t (which I have purchased in the past) does not have good performance at 10 Meters.

It seems that I should investigate the commercial offerings, asking:

How many beads or cores?Physical size of the beads or cores?Are they Mix 31 or 43?What type of coax or wire is used internally?What is the Rs of the choke at 10 Meters?

Does that sound about right?

TNX and 73, Rich, N6KT

    On Sunday, December 25, 2022 at 12:00:57 PM PST, Jim Brown <jim at audiosystemsgroup.com<mailto:jim at audiosystemsgroup.com>> wrote:

 On 12/25/2022 8:15 AM, Lux, Jim wrote:

> The material datasheet claims 20% uncertainty in the properties

> (although I don't know if that is "run to run" or "piece to piece

> within a run") - They're sintered from a powder, and having just

> looked a a bunch of micrographs of gas line filters made using a

> similar process, i was surprised how much variation there is in that process, within a batch.

I accumulated a stock of 100 or so cores purchased from different vendors over almost 15 years. They included one that was a pre-production sample from 2004-5. As part of my process, I characterized all of those cores by measuring the "same" winding on each of them, and tabulating complex data at selected frequencies. Cores were generally not labeled by purchase date, except for group of recently purchased cores.

After completing work on the Cookbook, I decided to try to evaluate Steve's recommendations for chokes on #52 material, and purchased 40 of those cores, buying 10 from four industrial vendors over about 8 weeks.

I repeated the characterization process, selected four cores at limits, wound and measured chokes based on Steve's designs for single core and two core chokes. I could not repeat any of Steve's recommendations with those "limits" cores.

73, Jim K9YC

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