[Amps] More parasitic choke questions

[Steve]

Maybe we have different ways of visualising what the suppressor is doing 
and how it does it. With regard to stability, I wasn't meaning the few % 
of tolerance or temperature drift, but the factor of 5 or more that I've 
seem with carbon comps after prolonged service at high temperature. They 
probably go even higher just before crumbling into dust.

Inductance - those are the numbers I recall, but I can't promise my 
memory isn't playing tricks these days. I probably posted the figures so 
it might be in the archives somewhere. What values do you measure?

Steve

Alex Eban wrote:
> None of these apply!
> All these resistors are meant to do is lower the Q of the suppressor
> inductance and dissipate the harmonic energy involved. Their stability is of
> no concern, since the circuit is not so critical as some believe.
> On the other hand, composition resistors have the lowest parasitic
> inductance of the generally available resistors and this is definitely an
> important characteristic, since this inductance can easily hamper proper
> suppressor operation. 
> BTW, your inductance measurement is off:  a piece of wire one inch long is
> approximately 25-30 nH, not 2-3nH. You have to add it to the resistor's
> inductance. You simply can't connect it with zero length wire!
> Alex	4Z5KS
> 
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Steve Thompson
> Sent: Tuesday, July 27, 2010 8:36 AM
> To: amps at contesting.com
> Subject: Re: [Amps] More parasitic choke questions
> 
>> It does seem though as
>> if the preferred carbon composition resistors are no longer easily found.
> 
> What is preferred about carbon comp? Given the heat and the need 
> for long term stability in value they're the least suitable 
> component you could choose.
> 
> Some years ago I measured some different suppressors(results in a 
> posting on 30 Aug 06), subsequently I swapped the carbon comp 
> resistors for MOX on a couple of them, and couldn't measure the 
> difference. Whenever I measure 2 or 3W MOX resistors in the 20-100 
> ohms range, the inductance is in the regions of 2-3nH, which has 
> minimal impact in a suppressor. Inductance is higher in the 5W 
> ones I've tried.
> 
> Steve
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