4-1000A grid driven transmitter layout

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K3YA:
I think Satan will stand behind you, whispering in your ear "Turn it up.  Look how the tube glows at 1500W carrier out."  He will say it over and over again to you.  Just like he does to me. 

Do you have the mod iron?

N4LTA:
I have had that happen to me before with a 6 meter 4CX1500 amp!

I have a Gates mod transformer good for at least 300 watts removed from a Gates BC transmitter - enough to get a whisper from ole Satan.


Pat
N4LTA

The Slab Bacon:
Think what you want, say what you want, the 4X1 is probably the best bang for the buck out there. Big power, usually cheap to find good used ones, and rather undemanding and very forgiving as long as you stay on the lower bands with it.

They are easy to work with, and look soooo sexy with a nice glow on the plate.
For the high bands those "ceramic jet engines" are the ticket, but down on the lower bands the 4X1 will always be my favorite. The biggest problem of building with them is that they are a rather large bottle. (but that just adds to the kool factor)

N4LTA:
Slab,

Is yours grid driven and swamped. I have seen circuits that use a 200 ohm swamping resistor and a 4:1 transformer to feed the grid.


I have the tube, sockets and the chokes and transformers and the variable caps. About all that I need are the PS filter caps and I think I have them covered. I could probably use a spare tube.

I'll likely use a pair of 813s to modulate it unless you convince me to go with screen modulation.

Pat
N4LTA

KM1H:
Quote

I think Satan will stand behind you, whispering in your ear "Turn it up.  Look how the tube glows at 1500W carrier out."  He will say it over and over again to you.  Just like he does to me.

I sucumb to that urge whenever a LK-800, AL-1500 or similar comes in for service :o  There is just something about having 1500-2400W of Pd at your disposal that makes me forget to turn the coax switch to the big Bird load ;D

I was stress testing a repaired LK-800NTC a few times last week on AM; I dont think the guys I worked believed I was just limping along at a 300W carrier from the LK-500ZC by the reports I was getting   ::)

Getting back to the 4X1; it requires a lot of RF voltage swing for Class C grid driven and a lot less in AB.  AB2 works OK IF you are using the GM3SEK tetrode boards or similar to keep the IMD manageable. AB1 makes the input circuit even easier as youre not dealing with drive power; just voltage. Ive built them both ways 160-10M and they put out lots of power, stable, and reasonably clean IMD. Several are still in use on the bands altho I quit building them around 1993-95 or so as local pulls dried up. Then did some 3CX3000A7s for a few years...now there is a fine tube for any mode you want, even brand new the Chinese ones are around $700 and very reliable in BC service.

And if you ever plan to use a MRI pull of any type you better start collecting them now as MRI is rapidly going all SS and sources are drying up fast and prices going up. Ive already put a little stash aside ;D

Carl

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