[Amps] Alpha 77dx L5 help

[Michael Tope]

Hi Jim,

My only familiarity with iron powder is there common application in 
high-Q RF inductors. They are available in a wide range of sizes 
depending on the power level involved. I don't know if they have any 
useful application for RFI suppression at frequencies above their 
intended application range.

73, Mike W4EF................

On 12/5/2024 1:47 AM, Jim Brown wrote:
> 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.
>
>
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