>From: Rich Measures <measures@vc.net>
To: <amps@contesting.com>
>Date: Thu, 24 Jul 97 02:15:00 +0000
>
>>>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.
>
>I've seen plenty of 811A's and 812A's. I've seen 100TL's and
>100TH's also, right up to 450 TH's and TL's....snip...
Yes indeed, and the total IMD level was probably -20db. The all-time
record that I measured was -11db.
>I really don't understand all the fuss and argument.
>
I realize this.
. ...snip...
>
>>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, just so we don't have to take your word for it, please quote
>for us the page number and text where Eimac states tubes with the
>suffix A3 are not recommended for grid driven service. .....
>
Grid-driven is perfectly okay for a medium-Mu triode---provided that
linear amplication is not the objective. The only type of triodes that
Eimac recommends for grid-driven linear amplifier service are low-Mu.
The reason is that at zero grid-v, only low-Mu triodes are capable of
drawing sufficient anode current.
Rich---
R. L. Measures, 805-386-3734, AG6K
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