Hi Phil:
My answer is: (g) - not sure.
G2DAF would be the only person who could properly respond, and he has been
on a dx-pedition for years. Unfortunately, the G2DAF amplifier is not of
sufficient power to allow him to "get out" from his present location, even
though his final has handles.
Since G2DAF was a designer at Mullard, we must give him some credit for not
using a tube improperly. The tube he used was similar to a 4-125 and would
have been designed for linear service (at least as a modulator). The
operation of the G2DAF was not desgined to get more output than in "normal"
service, but did save money by eliminating grid bias and screen supplies.
Although that design was novel, I believe the same tube could have been used
in grounded grid service with additional savings in components.
Additionally, grounded grid offers additional inverse feedback which reduces
distortion. I do not yet know if this particular tube (or other similar
tetrodes) were used in grounded grid service at the time of development of
this design. That might be an interesting question, though.
Today, perhaps there are just a few reasons to use the G2DAF circuit. One
would be to experiment and the other would be to use surplus tetrodes which
might not be usable in grounded grid. In respect to the latter, the savings
would be in not needint a screen supply and grid bias. But, that is where
the debate continues.
Colin K7FM
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