Grounded Grid Amplifier Design. When Did it Become Popular?
Most of the publications I like to read while on the throne, are old technical books or journals. My latest is an old 1962 RCA Transmitting Tube Manual. In the back of the manual are circuit examples of the use of these power tubes in various RF power circuits and most are triodes but not a one uses grounded grid design.
I may be mistaken, but many if not most of todays high power tube amps using triodes are grounded grid design. Correct me if I am wrong about that. But my question is, when did grounded grid design seemingly become the defacto design for today's high power RF amps? What was the impetus or discovery that made GG popular?
It may have come in the late 50's or early 60's with the acceptance of SSB mode for the majority of Amateur fone ops.
The grounded cathode is a much more efficient mode and suited for high power high level AM .
My old "Editors and engineers handbook" (Bill Orr) 1960 Ed had Grounded grid designs that I incorperated into my Home brew 4X811a tube KW amp.
It seems easier to drive with a medium power 50 ohm output designed transitter.
Last edited by K8JD; 08-10-2012 at 12:03 AM.
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The introduction of the Eimac 3-400Z (Z = zero bias) in 1961 was probably the turning point.
One factor was the availability of exciters that could drive a GG design. Many of the exciters in the 50's were 10 or 20 watt critters. As higher power exciters became the norm, GG amps that could be driven with 80-100 watts became more common.
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Tubes that work well in GG go way back, like the 811A which was around 20 years before I was born.
But it's true that for AM plate modulation and for CW, there was really no need for GG designs.
So I'd say GG designs coincide with SSB popularity. Collins pretty much introduced SSB to the mass market in the 50s. So, prior to that, really no need for it.
The first "popular" Collins SSB transmitter, the KWS-1, used a pair of 4X150s and they weren't grounded grid. But the 30L-1, part of the "S" line, was.
Many amps in the 50s weren't, either...like my old Johnson Thunderbolt (2 x 4-400s), which was a grid-driven design. By the 60s, HF amps were going GG. The 3-400Z I'm sure helped.
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For a long time, there weren't many tubes being made that would work well in GG. You really need a high-mu tube, that is, with a high enough amplification factor for a cathode-driven GG amp.
Maybe some tube engineer somewhere got tired of neutralizing amplifiers, and that was a motivating factor. :-)
GG amps need more driving power and had to wait for 100 watt exciters. GG amps have better IMD performance (due to cathode degeneration) and the increasing use of SSB made this more desirable. And GG amps are just as efficient as GC amps, so no trade off needed there.