>
>Tom has some very good points. Personally, the G2DAF is not an approach I
>would use, but it can be made to work. My feeling is that some tubes work
>better in that circuit than others; the screen grid time constant needs
>careful consideration, and the effects of the rectifier on the effective
>grid loading are not negligible. I suspect atube that was very low
>distortion in screen modulated AM would be the best performer. Whether the
>approach can, under optimum conditions, be made to work adequately well for
>today's bands is another matter. I am certainly unconvinced that any tetrode
>can be just stuffed in and produce acceptable or better results.
>
>I cannot accept that grid current is always, under any and every condition,
>tube and circuit, is of necessity going to produce too high a level of
>distortion.
Can you accept what is on the constant-current curves?
>
>
>>The operating point moves all over the place with tuning and
>>loading, as well as drive.
>
>This is where the G2MA circuit, which effectively used a clamp tube to
>modulate the screen, won out; the variable RF loading was reduced to merely
>a control voltage. However, I still believe that a tetrode with suitably
>regulated screen and bias supplies, operated with a low grid RF source
>impedance, and RF negative feedback, in a conventional circuit, is a
>superior product to a G2DAF approach.
>
>I figure that Rich and Tom will probably agree there!
>
I do not agree. Modern transceivers need a 50-j0 ohm load. With grid
current, the load Z on the exciter goes bananas
>
later, Peter
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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