[Amps] Maximum RF output in practical application: 4-250A

[R L Measures]

On Jul 2, 2006, at 1:42 PM, wc6w at juno.com wrote:

>
>
> -- R L Measures <r at somis.org> wrote:
>
> <snip>
>
>>  was the plate/anode white hot?
>
>
> Hi Rich,
>   Not if the tube is operated at 90% efficiency.

And if the 4-250A is operated at 110% efficiency in high humidity,  
frost will form on the envelope during lengthy transmissions?

Seriously, Marv,  after looking at the constant-current curves, I  
don't see how 90% is do-able.
>
>   You may want to review Kahn's Envelope Restoration technique in the
> Proceedings of the IRE, Vol. 40, July 1952, pp 803-806
>
>   Some further details are shown in the Proceedings of the IRE, Vol.
> 44, December 1956, pp 1706-1712.  The curious may wish to recalculate
> the numbers in Appendix One with a 90% efficient RF power stage, in
> lieu the 80%, plus a 90% efficient Class D audio modulator instead of
> the (55% efficient) 1950's vintage Class B stage.
>
>   An article describing a 90% efficient RF stage is posted on my
> webpage at:
>
>   http://wc6w.50webs.com/wc6wamps/index.html?fr422.html
>
> Soooo...now, how much power does the plate have to dissipate, running
> 2KW peak, if it's 90% efficient?  Don't forget that the average power
> of a (two-tone) SSB signal is only half the peak.  The tube won't even
> glow.

I do not believe that 90% is possible in a linear amplifier that can  
be QSYed.   At 14-cents per kWH, the yearly operating cost difference  
in my ARS between 60% and 90% would be under a US$.  .

cheers, Marv
>
> <snip>

R L MEASURES, AG6K. 805-386-3734
r at somis.org