>At 03.38 1997-12-22 -0800, you wrote:
>>>>Grandfather Measures used to say: "There is no such thing as a free
>>>>lunch."
>>>
>>>Rich,
>>>
>>>Are you suggesting that things have changed, and that there is such a
>>>thing as a free lunch?
>
>AG6K:
>no. The g2daf promises a free lunch. There is no free lunch and no
>Class C linear.
>
>Wrong. G2DAF never promised a free lunch (at least not for me....)
It promised higher efficiency in a linear amplifier. It delivered higher
effiency. The trade-ff was linearity.
>Right. I agree that there is no linear class C amp, but with floating
>class of operation there are several examples...
The only class of grid driven linear service is AB1 -- {although the
4cx1500B and 4cx600J can tolerate up 0.5mA of grid current, yet remain
linear}.
... ... ...
>Not that you have asked for it, Rich, but I guess I cant resist to send
>you the plotted linearity-graph (using HP spec.) as a special xmas gift
>for You! ;)
>
Thanks, Lars. I read the graph over. However, the IMD test that really
counts is dynamic -- i.e., how many db down is the SSB voice splatter in
the two windows adjacent to the fundamental signal. This is what your
fellow amateur radio operators are going to hear.
- It seems to me that grid bias supplies and screen supplies are pretty
easy to build. The AB1 bias supply produces zero current, so regulation
is not needed. The 723 IC and power FETs make screen regulation a piece
of cake. 60% vs. 75% efficiency hardly makes a difference on the Rx
S-meter.
Rich...
R. L. Measures, 805-386-3734, AG6K
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