[Amps] Amps Digest, Vol 264, Issue 7

[John Lyles]

Powered Iron makes low loss toroids but are not useful as EMI 
suppressors. The inductance and the net impedance is low also. As we all 
know, ferrite works very well if you get the right mix.

73

John

K5PRO

> Message: 1
> Date: Fri, 6 Dec 2024 07:16:22 -0800
> From: Michael Tope<W4EF at dellroy.com>
> To:amps at contesting.com
> Subject: Re: [Amps] Alpha 77dx L5 help
> Message-ID:<e7306fd4-bce1-4987-bf69-311b1afd25e1 at dellroy.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> 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.
>