[AMPS] Re: Parasitics

[Ian White, G3SEK]

Rich Measures wrote:

[G3SEK wrote:]
>>The original parallel circuit disappeared in step 2 when we transformed
>>it into its series-equivalent. There is absolutely no bar to treating
>>the series-equivalent circuit just like any other series circuit.
>
>I do not believe it. 

Excuse the smiles from British readers... "I don't believe it!" is the
catch-phrase of a highly successful TV sitcom called 'One Foot In The
Grave'.

> 
>>
>>By the way, if the move I made isn't "legal", all your pi-tanks just
>>stopped working!
>>
>A pi-network tank is not the same thing

It works on exactly the same principles. There's an example calculation
on the NETAN web page which includes precisely the same operation that
you object to. 

In that case it is the load resistance (50 ohms) paralleled with C2.
That is changed to series-equivalent form, and added in series to the
reactance of the pi-inductor.

If that operation was not "legal", the pi-tank wouldn't work. But it
does work, and gives exactly the predicted impedance transformation.
Therefore... QED.

>>--------------------------------------------
>>
>>>Your calculation of how the 100ohm suppressor R became 49 ohms at 10MHz 
>>>in Wes' measurements would interest me. 
>>
>>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, 
>
>Wes' table is not in my Web page.
>
My mistake: it's actually from one of Wes's own pages, downloaded and
filed with some of yours... though I coulda swore that you had a copy of
the whole table on your site at one time... anyhow, it's the same table
that we all refer to. 

(BTW, in case anybody thinks I'm fanatically archiving all this stuff,
I'm not. We have to pay for phone time by the second over here, so I
routinely download interesting web pages for study off-line, and keep
most of them out of sheer inertia.)

>
>Rp is 49.26 ohms.  The 100 ohm suppressor R is in parallel with the 
>95.6nH suppressor inductor, which Wes calls Ls.  93.46 ohms is not the 
>resistance of the suppressor R.  

On that subject I think we're all out of step except you, Rich.

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.demon.co.uk/g3sek

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