[Amps] QEX Innovative Tube Linear?

[Will Matney]

Peter,

Yes, your correct. You can run them above the design-maximum ratings. However, when they go poof, the manufacturer wouldn't back them up, nor would a bunch of suppliers at the time. There was a few ham manufacturers who made what supposed to be a 1 kW input amp using 4 6JE6's, and ran the plate voltage upwards of 1200 Vdc. When the tubes went poof prematurely, the user had no place to turn. I guess they figured back then that as cheap as the tubes were, buying 4 wouldn't be a problem (6JE6's were about $8-$10 each US in quantity). If they had ran them at a lower voltage, say 900 Vdc, and used about 6 tubes instead of 4 for the 1 kW input, they would have had a good service life. Raising the plate voltage, as you know increases the amplification, so that was needed to get 1 kW input out of 4 tubes. I've seen 6JE6 tubes ran at 750 Vdc with good linearity. The tube manufacturer wouldn't have backed the 6JE6 tube anyhow in RF service, but would have the two I mentioned earlier. The suppliers warrantied them though, but after finding out what they were being used for, refused to warranty them. Radio Shack was one case. The problem here was a few amp manufacturers tried to make an amp as cheap as possible, not caring about tube life, which is my opinion of course.

Best,

Will


>*********** REPLY SEPARATOR ***********
>
>On 7/8/06 at 3:16 PM Peter Chadwick wrote:
>From memory, sweep tubes are rated for several kV of plate volts during
>the pulse, so breakdown (flashover) isn't a problem per se. . This
>suggests that provided you don't exceed the dissipation, you can run a
>high plate volts and have a good swing above the knee of the curve, and
>arguably, better linearity.
>Exceeding the plate dissipation is another matter altogether, and is I
>suspect, done at the expense of tube  life if not linearity. It is amazing
>what you can get away with tubes though: remember the early radars that
>really hammered tubed not designed for pulse service.
>73
>Peter G3RZP