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[AMPS] construction of parasitics

To: <>
Subject: [AMPS] construction of parasitics
From: (2)
Date: Wed, 25 Jul 2001 10:00:56 -0700
>>>I can use a series of measurements to determine the approximate
>>>value of R and L in most cases, but I've also found many cases
>>>that require testing of several PA's to optimize suppression. A
>>>simple formula would certainly save work!
>>/\   First off, one needs to realize that roughly equal currents need to
>>flow in L=supp and R-supp at the anode's VHF resonant freq.

>Why is this ratio optimum? I would have expected to get greater damping if
>you put a higher percentage of the current through the resistor.

/\   The L/R VHF parasitic osc. suppressor has two current paths.  Since 
the magnetic fields from these two currents are at right angles to each 
other and the inductances are not equal, a staggered-resonance effect is 
produced.   This tends to decrease the Q of the (virtually unavoidable) 
VHF resonance in the anode circuit.  Because the peak E amplitude of the 
damped-wave ringing is proportional to the Q of the resonant circuit 
multiplied by delta-I, lower Q (and Rp) tends to increase stability.  By 
dividing the VHF ringing current equally, neither resonance dominates the 

cheers, Steve

-  R. L. Measures, 805.386.3734,AG6K,  

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