[Amps] Old Transmitter designs (was cathode driven/groundedgrid magic revealed.)

[Fuqua, Bill L]

Even if the grid did not draw current there would be an non-linear input impedance on the input of a cathode driven tube amplifier.
That is because the plate current in not linear with grid-cathode voltage but something like Vin(t)^3/2 during the positive swing of the grid-cathode voltage or 
negative swing of the input (cathode-ground) voltage.  Since the cathode current is the same as the plate current the V/I curve is non-linear.
True, grid current would make it worse but is not the only reason for the non-linearity. 
   You could make a grounded grid AB1 amplifier with a 304TL which would require a lot of negative grid bias. You could connect the grid to ground and make the cathode positive by several hundred volts and call it grounded grid if you like. Just don't allow the peak drive voltage to exceed the Bias Voltage.
Think about it.
   The term common-grid is probably less debatable than grounded grid. Or call it RF-Grounded Grid. But to me they are really all the same. 

73
Bill wa4lav 
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