>
>
>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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