[Amps] Swan Mark 1 on 160 meters

[gudguyham]

How does a torrid used on 160/80 meters get hot on 10 meters if it’s shorted out?


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On Wednesday, June 30, 2021, 2:42 PM, Jim Brown <jim at audiosystemsgroup.com> 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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