Do you use a roller inductor or switched tank coil assembly for your output network? Manufacturer brand that you use?

What kind of output power are you getting from your amplifier? Is it a grounded grid design? How much voltage are you using to feed your final?

I haven't built anything with a 4-1000, but do like the versatility of a rotary inductor. MFJ sells the component parts of their amplifiers, so you might find something usable there.

single 4-1000 tube will require some impedance tweaking on the input side, but they're good tubes.

Good to about 6kW with enough supply current and voltage. I seem to remember eimac 4-1000 tubes really liking about 6kV and 0.7A, and easily putting out a couple kW. Of course, if you run them down with about 4kV you'll get more manageable power output (and won't kill so many baluns and feed lines.)

ETA: Here's a good write up http://www.hayseed.net/~jpk5lad/4-1000A%20Amp/Building%20the%204-1000A.htm

I also like the versatility of a roller inductor.

Allows one to dial up any frequency within its range. One must use a turns counter though, to keep up with where one wants to operate.

Sometimes though, I think about the ease of just switching a tuning knob on the output network and going with that.

"single 4-1000 tube will require some impedance tweaking on the input side"

I have a good schematic to an input side impedance matching network that will work with the tube.

Thank you for your comments and insight!

6 KW for one tube?

I can make the power supply easily run 6 KV and handle the current requirements needed to get that kind of power but I didn`t know that that tube would do that kind of wattage.

Or take a cue from your average automatic antenna tuner, and use a bank of binary-weighted relay-switched fixed inductors.

Drive the relays with a simple microprocessor connected to a rotary encoder, drive a couple of 7-segment LEDs to display the number of "turns" currently on the rotary encoder, and you'd effectively have the same thing as a roller inductor with turns counter.