On Thu, 24 Jul 97 17:25:27 -0700 Rich Measures <measures@vc.net> writes:
>>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.
How can you demand others to supply absolute values one minute and then
say "probably" the next Rich?
The worst I can remember was the Swan 700 at -15 and the WRL 2000A at
-13dB.
>
>. ...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.
That is wrong.
Since when is the 3CX3000A7 low-Mu?
I also mentioned to you the other day about Bill Orr's 1965 article. I
suggest you read it since it will give you a better insight into the
issue. He also stresses the requirements to make a GOOD AB2 triode amp.
73....Carl KM1H
>
>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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