[AMPS] Re: Parasitics

Jon Ogden jono@webspun.com
Fri, 15 May 98 19:10:08 -0500

>That's presumably your pure-nichrome/100-ohms suppressor, which had a
>measured Rp of 49.26 ohms at 10MHz. (I'm copy-and-pasting these figures
>straight off Wes's table in your web page, to avoid any more typing
>On its own, the pure-nichrome inductor looked like 95.6nH (Lp) in
>parallel with 93.46 ohms (Rp).
>When shunted with a 100-ohm resistor, the Rp of the network is simply
>calculated like resistors in parallel - after all, it *is* resistors in
>parallel. That would be 1/(1/93.46 + 1/100) which is 48.31 ohms. In
>principle, Lp would be unchanged from its previous value of 95.6nH.
>Given that we've assumed ideal behavior, that prediction agrees very
>well with the measured values for the shunted suppressor: 
>Rp = 49.26 ohms, and Lp = 93.9nH. Actually that is better agreement than
>we're entitled to hope for, given the importance of stray series
>inductance... just lucky, I guess.

I think that's pretty cool!  It shows that Rich's supressor idea *DOES* 
indeed work.  In a sense you are getting extra resistance out of the 
inductor.  And that extra gives you a lower Rp which means lower VHF gain!

Guess those guys in the 1930s who used resistive wire knew a thing or two!



Jon Ogden


"A life lived in fear is a life half lived."

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