There's nothing subtle about a GS35b. See
www.qsl.net/g8gsq/gs35a.jpg and www.qsl.net/g8gsq/gs35g.jpg for
pics of a dead one that I opened up.
If the 8877 is a Ferrari, the GS35b is a sidevalve V8, or maybe a
diesel tractor.
Steve
> I suspect the difference is probably in the grid structure. This tube was
> originally designed as a radar pulse tube and is no doubt optimized for that
> service, not for linear amplifier service. I have not taken one apart, but I
> would bet the grid does not have the fine control over emitted electrons that
> an
> 8877 does, for example. Some of the electrons slip by, so to speak, and do not
> effectively contribute to the RF output. Thus the lower efficiency.
>
> Old timers will recall the receiving tubes from years ago that were designed
> as
> "variable mu" or "remote cut-off". Their grid structure was make of wires with
> uneven spacing so the gain changed with different bias levels. Something
> similar
> may exist in the design of the GS-35b.
>
> This is just a guess and should be taken with a grain of salt until the real
> facts are known.
>
> 73, Bill W6WRT
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