[Amps] Alpha 77dx L5 help

[Jim Brown]

Thanks Mike.

I don't know much about those materials, but I've learned a LOT about 
ferrites, which are quite different.  Ferrite cores exhibit 
self-resonance, and within that frequency range, are quite useful for 
suppression -- i.e., EMC. Many ferrite mixes that have useful 
conventional inductive circuit properties (that is, as cores for 
inductors) at low frequencies have self-resonances that are useful for 
suppression at higher frequencies. And these resonances, which mostly 
are in the VHF range for single turns (that is, one pass through the 
core), can be moved down (as far as 160M) by winding multiple turns 
through the core. That is the basis of my work on common mode chokes.

For a lot of reasons, Fair-Rite #31 is the only mix I've found that is 
useful at HF. Another great researcher, who has chosen to remain 
anonymous because he works in major labs where professional jealousies 
can be  a problem, was a VERY important contributor to my work. I 
continue to thank him for it.

73, Jim K9YC

On 12/4/2024 10:31 PM, Michael Tope wrote:
> FWIW, the pertinent technical data for the Micrometals #2 Iron Powder 
> material mix (relative permeability, mu = 10) can be found here:
> https://www.micrometals.com/products/materials/-2/
> 
> If you look at W6SAI's "Radio Handbook", a stack of two or three T200-2 
> cores is specified as part of the PI-L networks in several of the HF 
> amplifiers described therein.