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[AMPS] Re: Parasitics

To: <amps@contesting.com>
Subject: [AMPS] Re: Parasitics
From: jono@webspun.com (Jon Ogden)
Date: Fri, 15 May 98 09:45:47 -0500
>>Even if 
>>you do get say, 1 KOhm of impedance from all the inductances, that's NOT 
>>a REAL resistance.  That is a reactance.
>
>No it isn't. Think about your pi-network terminated in a 50 ohm load.
>The load impedance is transformed to say 2K across the tube - take away
>the dummy load and the 2K resisitive part disappears to infinity
>(ignoring network losses). Also, the 50 ohm resistor receives exactly
>the same amount of RF power as a 2K resistor wired across the tube
>would. 

Ok, this is true.  You are right.  The reactive components do the job of 
transforming impedances.  I wasn't thinking straight.  But my 50 Ohm load 
is on the OUTPUT of that transforming network, not in the middle of it.  
The supressor resistor is located a couple of inches or less from the 
anode.  The rest of the stray circuitry comes after it.  So looking from 
the tube out (which has a 2 KOhm impedance or so) how does that resistor 
which is effectively IMMEDIATELY after the output of the tube get 
transformed to some other value?  
>
>The same applies to a 100 ohm suppressor resistor, when it is
>transformed to represent 1K in parallel with the tube. It will dissipate
>exactly as much power as a 1K resistor connected across the tube. In
>that sense the 1K is a real resistance.

Still, call me dense, but I don't understand how this works.  I see no 
reactive impedance transforming network between the output of the tube 
and the supressor R.  Just a staight piece of brass, copper, nichrome or 
whatever your poison is.

73,

Jon
KE9NA



--------------------------------------------------------------------------
Jon Ogden

jono@webspun.com
www.qsl.net/ke9na

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


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