From: Rich Measures <measures@vc.net>
To: <amps@contesting.com>
Date: Fri, 25 Jul 97 00:25:27 +0000
>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.
Of course youn forgot to mention when the tube is neutralized, the
anode grid capacitance effectively goes to zero.
>>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.
Interesting you know the IMD level of amps from the 60's and
earlier, yet when you discuss your big grid driven 13 kW PA you
quantify IMD via over the air reports
>Grid-driven is perfectly okay for a medium-Mu triode---provided that
>linear amplification 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.
While I CAN find specific text saying grid driven tubes can be
A, AB1 or AB2, B or C...... I can't seem to find your claims
written anywhere.
What page of what book can I find that on please?
73, Tom W8JI
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