SV: SV: [AMPS] Final..

[measures]

>
>
>Rich wrote...
>
>> > I do not agree.  In AB1, the grid looks like a capacitor.  
>> > 
>
>To which John replied...
>
>> Now you got me!!!!!   How the hell can one develop power into a pure 
reactance?????
>> Surely the grid of a tube biased for AB1 is resistive?
>
>My understanding is that one DOES NOT deliver power to the grid of an 
>AB1 amplifier.  The driving voltage is always such that the grid 
>is never driven into the region where grid current flows.  All one 
>does is charge and discharge the "input capacitance" of the tube.  
>If one refers to one of the ARRL handbooks, in the tube 
>charactersitics section, one finds "driving power = 0".  

Yes. 
>
>So the grid of a tube biased for AB1 is NOT resistive.  A good way to 
>make the input of such an amplifier appear as a constant resistive 
>load to the exciter (a good thing!) is to put a fixed non-inductive 
>resistor from the grid to (RF) ground.  The resistor dissipates 
>(wastes!) the drive power.  Another benefit of such a resistor is 
>that it enhances the stability of the amplifier.
>
 .  well put, George


-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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