>
>The second test with an 813 was somewhat discounted because I have no specs
>from anyone on what the distortion products are when grid driven with a
>regulated screen.
? The 813 is not linear in grid-driven service. For linear service,
G-G is the only game in town.
>Suppose they are -18 db 3rd order distortion. That would
>make the test meaningless.
? indeed.
>At least with the 4CX250B, I have the published
>standard of -25 db. That published standard is only 3 db less than the
>results you arrived at with the G2DAF - which is close enough for me to
>wonder about the test conditions and the standard.
? You seem to have missed the point that the -22db measurement was
relative to Peak Envelope Power. Eimac does not use this reference
point. -24db Eimac = -30db.
>
>A number of test questions arise. What was the time constant for charging
>the screen of the tubes? If there was a delay, there would be distortion.
>Suppose the screen voltage could follow the drive exactly?
? The only way that the screen will follow the drive exactly is to
connect the screen to the driven grid and disconnect the screen bypass C.
. This can be done up to very roughly 100kHz.
>Would the
>results have been different? What was the distortion of the amps in the
>"normal" giid driven configuration?
>
? For the 4cx250B amplifier, the distortion level with a regulated
screen and zero grid current was approx. -30db below pep. For the 813s,
they were eventually converted to G_G. The distortion level was approx.
33db below pep.
>I would never build a G2DAF amplifier and put it on the air without testing
>it under all circumstances. Perhaps that is the big drawback.
? There is no drawback if you stick religiously to the two-tone test and
wear a suitable disguise at ham gatherings. .
cheers, Colin
- Rich..., 805.386.3734, www.vcnet.com/measures.
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