On Jul 2, 2006, at 1:42 PM, wc6w@juno.com wrote:
>
>
> -- R L Measures <r@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@somis.org
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