OK, I've put Supercathode drive on hiatus, figuring I should start with
plain old triode-connected cathode-driven tetrodes.
There's plenty of published data on 4-1000A in triode-connection, so I
pulled out my curves and started figuring.
Once again, my understanding of the instantaneous voltages/currents are
thus (Please correct me if I'm wrong!):
0. Grid and Screen grounded.
1. Drive cathode
2. "Grid Voltage" on constant-current curves equals (-1)*cathode voltage
(i.e., when cathode is positive, since grid is grounded, Eg-k is actually
negative).
2a. Exact same argument for the screen.
3. To make it easy, assume a value for minimum instantaneous Eb. To find
instantaneous Eb at any particular angle, just DCEb-PeakSwing*sin(angle).
4. Using the "Three-Halves" power law...the quoted screen voltage on my
curves is 500V. So if Eg-k
is 300V (peak), at the peak of the driving waveform
a. I scale all voltages by 0.6 (300/500)
b. I scale the currents found at the scaled voltage coordinates by
(0.6)^1.5 (roughly 0.5)
All other portions of the driving waveform would scale smaller, since Eg-k
only gets smaller.
5. Figure out all the conditions using Chaffee formulations.
Well, here's the rub and I am just too dense to get it:
I know that the 4-1000A can do GG Triode-connected at 3000V/700mA plate.
So if Ib,dc is 700mA then the peak instantaneous ib should be around 2.1A.
But that 2.1A would be the scaled value of ib (since screen voltage isn't
500V, right?). So on the published curves, 2.1/(0.6)^1.5=4.2A. That's
like ridiculously off-scale on the published curves.
Any more cathode drive than 300V peak and the scaled values all go
off-scale too. Besides, it seems to me that 300V peak drive in GG is
unrealistically high anyway.
So either you can't do this at all the way I'm trying to, or I'm doing it
wrong.
???
Thanks for your patience!
------------
Scott Townley
nx7u@primenet.com
------------
Collector of:
Stoddard Aircraft EMI/RFI receivers and accessories
Big Parts for that Big Linear Amp
70's era RF test equipment HP/GR/Tek
Radio-related technical reference material 1940+
...anything else that will keep me off the streets at night
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