[Amps] Tube Class C operation no Drive power or grid current

[Fuqua, William L.]

    Maybe I have not looked at the data sheets very closely , but I was surprised to find a medium power glass Pentode that required zero grid current, thus no drive power in class-C operation.  The 4E27, not the A version. Pre-Eimac version. Eimac countered with the 4E27A which had greater plate dissipation and did require some grid drive power and current.
   Also, looking at suppressor grrid modulation. Efficiency about same with control grid or screen grid modulation and class B AM linear operation.
Advantage is that the AF suppressor grid impedance is infinite because it is never driven positive. The downside is that high screen ggrid dissipation is high.
That is because when suppressor grid is negative, current that would otherwise go to the plate is diverted to the screen grid.
   Just can't get something for nothing. Hi Hi Hi

Any other examples of zero control grid current glass tube class-C operation any of you have found.

73
Bill wa4lav