[Milsurplus] AN/SRT-4A Marine Transmitter

[Kenneth G. Gordon]

On 17 Aug 2018 at 7:47, AKLDGUY wrote:

> Interesting observations on beam tubes as oscillators.

Both the Orr and RSGB handbooks make this point also

> What about when the screen is strapped 
> to the plate, effectively turning it into a triode? Or did you mean that too?

No. I haven't thought about that part of it.

I was referring specifically to the ECO. The Electron Coupled Oscillator, in which the screen 
is supposed to be acting as the "plate" of the the triode formed by it, the grid, and the 
cathode.

In the ECO, as you know, the electron stream from that "triode" oscillator then couples itself 
to the plate circuit, the screen also acting, more or less, as a shield between the grid and 
the plate.

This results in greater stability of the oscillator, and the parts of the tube after the screen 
grid essentially act as a buffer amp.

Beam tubes, by their very design, completely negate this characteristic, since the 
beam-forming plates couple any signal at the grid (or cathode) of the oscillator-proper 
directly to the plate, bypassing any "shielding" effect the screen might be able to offer.

Thinking about it now for a bit, triode oscillators are a different matter. If a beam-tube was 
triode-connected (depending on the connection: screen to plate or screen to grid) there 
would be no ECO action and therefore it shouldn't matter. "Shouldn't", I would guess.

Ken W7EKB

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