Ian White GM3SEK wrote:
Ken Scharf wrote:

A single 4cx800 will get you close to the legal limit.


That's being over-ambitious. The manufacturer's data (Svetlana) says
that a single 4CX800A "will conservatively produce 750 watts PEP SSB,
and 750 watts Key Down CW in any of the three modes: grid-driven,
grid-driven passive input, and cathode-driven."
http://www.g8wrb.org/data/Svetlana/pdf/4CX800A.pdf

You can certainly screw more power from the tube, but intermodulation
levels will rise rapidly. When selecting a tube, a good rule of thumb is
to expect an RF output equal to the tube's anode dissipation.

If the original aim was for something "in the region of" a kilowatt, it
would be well worth considering a single 4CX800 at slightly reduced output.



I didn't have the data sheet in front of me, but I just assumed that
with a plate rating of 800w it would max out near 1200w out.
The 3cx800 tube will put out this much and there are single tube
amps using this bottle that will do that. Guess the 4cx800 is a
bit short on the plate voltage or max cathode current rating to
make it to 1200w.

Well you could use a pair of 4cx800's to get to 1500w out if that
is your goal. A pair of these are STILL cheaper than a single
4cx1000a or 8877 (especially with the cost of the sockets
figured in).