[Amps] Thinking out loud

[Vic K2VCO]

I'm thinking out loud, I guess it's called brainstorming. Just hit DELETE if it's boring!

I already have just about all the parts for my amplifier, which will use a pair of 813's, 
but before I do too much construction I need to settle on the design :-) Since I only 
operate CW I had decided to go class-C, which would easily produce 750-800 watts from 
these tubes.

I had decided to use a conventional grounded-cathode circuit with a link-coupled 
parallel-tuned input.

This means that the drive required will be on the order of 10 watts. No matter how careful 
I am, I can guarantee that the day will come when I hit it with the full 100 watts from my 
exciter. So I would want to do something simple to protect the tubes. Should I use

1) A grid trip circuit that will open the ptt line on excessive grid current,
2) A screen trip circuit, etc., or
3) Something else?

Another possibility is to switch to grounded-grid. I am not sure what the issues would be 
in trying to operate a gg amp in class C. Would I have to do more than just lift the grids 
from DC ground and supply appropriate bias and screen voltages? In particular I want to 
provide a good SWR for my solid-state transceiver, and I don't know what the input 
impedance would look like in class C.

Finally, I could give up on the idea of class-C. In that case I could use a G2DAF circuit 
in which the screen voltage is derived from the drive. This has the advantage of a simple 
swamped input which would provide a good swr to the exciter, and elimination of the screen 
supply. But then I can expect only about 600 watts.

I looked into running a G2DAF or other swamped input amplifier in class C, but it would 
need a very large amount of drive across any reasonable value of swamping resistance to 
get adequate RF grid voltage -- a 1000 ohm resistor would be needed and it would burn up 
about 75 watts just to get the grid swing (and that doesn't include the screen power for 
the G2DAF design).

I'm looking for ideas.
-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/