>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.
>
Good point, Mr. Rauch. Nevertheless 1000v of grid drive across a 100pF
grid takes a bit of doing.
>>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
>
I measured the total IMD of the 8171 Class AB1 amplifier with the
step-attentuator method, using H-P 355 step-attentuators.
Rich---
R. L. Measures, 805-386-3734, AG6K
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|