[Elecraft] BL2 choking Impedence measurements?

[David Woolley]

Ian White GM3SEK wrote:
> CUTTER DAVID wrote:
> 
> Some UK suppliers do stock beads in #31 material but mostly not the ones 
> that interest us. I haven't checked in the past few weeks, but will need 

I'm fairly sure that Farnell did some #31 material, bigger than beads, 
but smaller than typical for amateur radio use.  I seem to remember you 
had to read between the manufacturer's catalogue number to work out it 
was #31.

> to refresh this information in time for the RSGB Convention.

I tried writing to the RSGB's EMC contact email addresses a few months 
ago, enquiring about sources of #31 material (and twisted pair speaker 
cables in less than whole drums, although I've found the latter and I'm 
waiting to see if it helps).  However the first address I tried bounced 
and the second one never replied, so I gave up.

I think the big problem is one of education.  Most people in the hobby 
believe that toroids are good, but probably don't even realise they have 
to be ferrite.  The RSGB's filter collection doesn't seem to have 
changed in a couple of decades, and the big traders, presumably 
successfully, sell EMC toroids without any indication of what they are 
made from.

>> What is going through my mind is how the amateur fraternity could 
>> persuade a distributor in EU to stock these and the type 31 cores.

In terms of the big electronics distributors, you probably have to 
convince them that there is a large commercial shortwave RF engineering 
industry in the UK, which may not be true any longer.  For the amateur 
equipment suppliers, you need to educate the market so they refuse to 
buy anything else.

-- 
David Woolley
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