The AM Forum

horse racing? There is a story on this page:
http://www.mossware.com/4x1000Amp_For_Sale_Or_Trade/
Is this what it is called? I suppose it is like a certain football game held on another band. I had no idea there was "Horse Racing".
A neat story anyway.

Can you run 10 KV on a 4X1???   

He said the PR ones. In any case you can certainly brag about having done so.

I've personally run 6.5.

Im still wondering how 10 kv at an amp equals 20 kw.

--Shane
KD6VXI

Shane,

I assume it is 1 amp per tube.

Pulse.

A staccato high squeaky voice...   ;D

Interesting thang about "pulse rated" tubes....   the 4PR-1000A (pulse version) uses exactly the same parts as a regular 4-1000A - except they are manufactured with more precise tolerance specs. IE, the spacing between the screen, grid, filament, plate etc is at tighter tolerances. This allows higher voltages that will not arc due to misalignment of elements relative to each other. It's akin to "blueprinting" a racing car engine.  We pay a good premium for the pulse rated tube, of course.

I have both tube versions here. I have never had a regular 4X1 arc over, though I limit my voltages to about 4KV for both linear or plate modulated service. (about 10KV peak on AM plate mod service)


* I just found a better description by Chuck K1KW from an old thread. Notice the "PR" designation goes on AFTER the tube is manufactured and simply a tube screening process:

"The "PR" version of a tube is mechanically identical to the non "PR" version except that it has gone through additional electrical testing to ensure the high voltage stand off required for Pulse Radar service among a few other tests.  You will notice a different set of specifications on the PR tubes data sheets since they were tested for specifications required for radar service.  Tubes, like many solid state devices today, had their final specs determined after manufacture.  For our service, you will not see a difference in a PR tube from a non PR tube."

BTW, the peak output power in linear service is usually limited by the plate dissipation of a tube. Sure, we can piss beat the tube and run 8KV and ridiculous power until the plates turn white and the seals shorten the tube's life. But it would be better to run a 3CX-3000A7 instead, or some other external anode version.  The IMD figures (side channel splatter) when running a 4X1 at 8KV and 5KW out must be abominable, approaching -20db 3rd order or worse.   These amps are for quick 59 - chow contacts and be gone... ;D

Another interesting point... I've been told by an Eimac engineer that the 4X1 is really a 1500-2KW dissipation tube when run with plenty of air. They are "rated" at 1KW dissipation by design, but are like an 813 - very conservative design.

I have six 4X1's in service - two in a homebrew linear and four in an AM homebrew plate modulated rig. They all run about 2-4KV, depending on my mood.

BTW, when a 4X1 is run over 5500V, there is a secondary plate bombardment bounce of the electrons that can cause distortion. (There is a technical term for it)    Run a 4X1 at 5500V max in linear service - and 4KV max in plate modulated service and we are fine.  Run it higher and the IMD splatter up the band may be the limiting factor.  

Big grid current drive, often used for these ridiculous power levels in GG, are rough on the tube and also produce poor IMD figures.

T

I used a 4PR1000 in my old "Pair-of-450TLs-modulated-by-a-single-4PR1000-Pulse-Width-Modulator" rig.  The power supply in that rig was 10kV (which put 4kV on the RF amplifier at carrier). 

Maybe a "regular" 4-1000 would have worked, since I did not at any time exceed 10kV, and a modulated 4-1000 with 4kV on it would reach 10kV on peaks of 150% positive...

I ran that rig for about 10 years before finally replacing it with an equivalent class E rig.  Interestingly, I was able to run the 4PR1000 modulator with no air on it, other than a small fan strictly to cool the filament pins.  The modulator was very efficient.