...snip...
>>2. Low Mu triodes are not appropriate to use in Class AB2
>>cathode-driven
>>linear amplifiers because they exhibit low gain.
>
>So what do you consider low gain Rich?
3 in 7 out. (3cx3000F1/A1 in g-g)
>What is your example of a good AB2
>grid driven triode?
810, 1000T, 450TL, et cetera---but not for linear service. The only
tubes I know of that are usuable in grid-driven Class AB2 linear service
are the 4CX600J and the 4CX1500B. However, the permitted grid currents
are less than 1 mA.
>Why do you continue to make such a big deal over driving voltages?
The grid has C. Developing 1000V or so across the typical grid's C at
28MHz is not a piece of cake. Another complication is that when you are
trying to drive a triode's grid in the positive-going direction, the
anode is headed in the opposite direction. Since the anode/grid C in a
3cx3000 is about 20pF, it is a big deal at 28MHz. Have you ever seen a
3CX3000A1 in grid-driven linear service at HF? I have not. The 4CX3000A
and the 5CX3000A, yes.
>...... The final system
>complexity is not much different from a 3CX3000A7 that requires 400-500W
>of drive in GG or a A3 version in grid driven service that wants 1000V+
>of grid swing.
IMO, the A3 would not be suitable for grid-driven linear service. Eimac
does not recommend it. The A1 would be suitable for grid-driven linear
service up to a few hundred KHz.
Rich---
R. L. Measures, 805-386-3734, AG6K
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