Rich says;
>Also, at say 14MHz, the grid is changing considerably faster than every
5uS.
I don't follow what that has to do with it. The screen volts follow the
envelope of the signal, not the individual RF cycles.
Same way as the Collins high efficiency solid state PA in the late 60's or
early 70's, that modulated a switching supply to vary the Vcc in sympathy
with the modulation envelope.
The original G2DAF used 7000pF total screen capacity; the diodes had a
resistance of between 5 and 12 ohms, depending on the current, and the
source impedance was lower than 300 ohms. So the tc would be around 2.5
microsecs. This suggest very little phase delay between the screen volts and
the RF envelope.
73
Peter G3RZP
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|