[TowerTalk] Wireman W2DU Current Type Balun

[Jim Brown]

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