[Amps] Swan Mark 1 on 160 meters

[Jim]

Jim

We were speaking of using toroids for RF TANK CIRCUITS.

Not common mode chokes.



Thanks
73
Jim W7RY

On 6/30/2021 1:41 PM, Jim Brown wrote:
> On 6/30/2021 5:34 AM, Jim wrote:
>> DO NOT use toriods. I speek from experiance. Had a reaction when on 
>> 10 meters with my 8877 amplifier. The 160 meter toriod coils would 
>> start smoking when on 10 meters. I was using a shorting switch.
>
> "Toroid" is a shape in which hundreds of very different materials are 
> manufactured. I know nothing about powdered iron toroids (although 
> they are very successfully used in the 5B4AGN-designed bandpass filter 
> kits I built years ago), but I know a LOT about ferrite toroids.
>
> The Fair-Rite catalog is a treasure trove for learning about ferrite 
> materials. The company has developed several dozen different chemical 
> mixes for very specific purposes, and there are mixes that can handle 
> a lot of power in specific frequency ranges. These mixes have been 
> assigned numbers. In general, these materials have low loss at low 
> frequencies, high loss at higher frequencies.
>
> Over the years, a few select companies have published technical data 
> and applications notes so detailed and filled with information that 
> you can learn as much from them as from colleges and technical 
> schools. Those published by RCA (tubes), National Semiconductor, 
> Electro-Voice (loudspeakers) are examples. The Fair-Rite catalog is 
> deservedly within this group.
>
> The catalog is here.
>
> http://www.fair-rite.com/files1/Fair-Rite_Catalog_17th_Edition.pdf
>
> Beginning on page 10, start by reading the brief description at the 
> top of the page for each material, then studying the graph of "Complex 
> Permeability vs. Frequency." On this graph, mu' is the purely 
> inductive permeability of the material, mu'' is the resistive 
> component, where R and X are in series.
>
> For example, in the first entry, #68, permeability is fairly low 
> (about 15), but loss is also quite low up to about 100 MHz, where it 
> begins to rise rapidly. The next entry, #67, has higher permeability 
> (about 25) and comparably low loss up to about 30 MHz. N6RK, a very 
> smart engineer who retired from HP some years ago, has used #67 
> toroids for high power transformers.
>
> Ferrite materials are useful as common mode chokes for RFI suppression 
> in frequency ranges where they are very lossy. #61 is useful as an 
> inductor core (including transformers) at HF, but starts getting lossy 
> around 10 MHz (where mu'' starts rising), and is sufficiently lossy at 
> UHF that it's useful for suppression.
>
> 73, Jim K9YC
>
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