> Not wishing to discuss the G2DAF circuit any further, I still want to
> question your statement regarding substantial grid current causing
> distortion. I do not think that is necessarily true.
Some tubes won't tolerate grid current, while many will. There are
dozens and dozens of tetrode types that can be run with a small
amount of grid current, and will give very good IMD performance.
The problem is not only anode current saturation, but it also
includes grid voltage to anode current change non-linearities
caused by grid intercept and other problems.
There also is the problem of a sudden change in grid impedance
with drive power.
AB2 SSB operation always requires a regulated low impedance
control grid circuit, and a well regulated screen supply of the proper
voltage. I do that in AB1 also, just to be sure if the tube is
"bumped" a bit hard it doesn't distort excessively.
I strongly question the wisdom of not only loading the exciter with a
changing impedance caused by control grid current, but
aggravating the problem by requiring the exciter to also supply
screen current through a rectifier system.
Maybe someone can explain to me how the screen voltage
remains exactly in phase with the driving signal, to prevent
envelope distortion from screen voltage shifting slightly out-of-phase
with drive?
Are tetrodes linear at all screen voltages with a constant grid bias?
73, Tom W8JI
w8ji@contesting.com
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