>At 08:11 AM 6/11/97 -0700, you wrote:
> IF you switch to a
>>different radio, reset the grid V for zero grid current with max.. RF
>>out. That's all, folks!
>
> No way Rich. Doing it this way will in many instances result in
>class "C" operation. ...
This scenario would only be possible, Jerry, if the Class AB1
amplifier was designed with an extraordinarily wide range of screen V
adjustment, and an ignorant operator adjusted the screen-V instead of the
grid-V.
For example, an 8171: grid bias V is -350v for Class AB1 and it is
-350V for Class C. How can you adjust the amplifier for Class AB1 or
Class C with the grid bias V adjustment, Jerry?
To change an 8171 amplifier from Class AB1 to Class C, the screen V is
reduced from 1500V to 500V. In the one I designed and built, the
regulated screen voltage was adjustable from 1000V to 1510V. To run this
tube in Class C would have required a separate 500V screen supply because
the power transistor used for the regulated screen supply pass element
could not safely withstand more than 550v drop. .
Similarly, Class AB1 grid bias supplies are designed for a practical
adjustment range. In a typical 8171 amplifier the grid bias adjustment
range would be roughly 275v to 400v. .
- -note- - Class AB1 adjustment procedure is described in *Amplifiers*..
http://www.vcnet.com/measures
Rich---
R. L. Measures, 805-386-3734, AG6K
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