[Amps] G-G Amplifiers With No Tuned Input.

[2]

Amplifiers such as the MLA-2500, SB-230, 374, 78, and 76PA have no tuned 
input.  This is not a problem when such a g-g amplifier is driven by a 
tube-output radio such as the TS-830S.  The reason is that although the 
input Z of a cathode-driven triode fluctuates from roughly 1/3 of the 
average driving Z on negative peaks to a virtual open circuit on positive 
peaks, the Pi-network tuned circuit in a tube-output radio acts as a 
flywheel to smooth out the Z fluctuation at the cathode/s.  However, with 
modern solid-state radios there is no tuned output, so something is 
needed to smooth the Z fluctuation.  A possible workaround, short of 
adding a bank of tuned input circuits, might be to put a ultra fast 
recovery diode in series with the input terminating R.  The diode is 
oriented so that the terminating R conducts only when the driving 
potential is positive -- which is when the tube is not conducting..  
Thus, on the negative half of the driving cycle, when the tube has a low 
driving Z, no driving power is lost in the terminating R and the driver 
should see a lower SWR.  
- -  Unfortunately, I do not own such an amplifier to test the idea on.  
If anyone out there has such an amplifier and is willing to test this 
idea, please inform me and I will send you a freebee 2A, 35nS, 300v 
switch diode.

thank you.

-  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K, 
www.vcnet.com/measures.  
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