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## [AMPS] construction of parasitics

 To: [AMPS] construction of parasitics 2@vc.net (2) Wed, 25 Jul 2001 10:00:56 -0700
 > >snip >>>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 picture. cheers, Steve - R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures. end -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesting.com Administrative requests: amps-REQUEST@contesting.com Problems: owner-amps@contesting.com
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