Phil, Rich, and Jim wrote,
> Subject: Re: [AMPS] 8877 bias curve?
>
> > >Here's a sampling, based on a constant plate voltage of 3900:
> > >
> > >Bias (V) Plate (ma)
> > >------------------------
> > >19.4 Cutoff
> > >18.0 18
> > >17.0 33
> > >16.0 51
> > >15.0 70
> > >14.0 92
> > >12.0 142
> > >10.0 198
> > >8.0 262
> > >
> > >Does this look anywhere close to real?
>
> Looks really close to me, Jim.
>
> > >
> > / As I read it, 8.2V of cathode-grid bias produces c. 185mA of
> > ZSAC. However, even at 90mA of ZSAC, an 8877 is so much cleaner than
> > today's transceivers, it would make virtually no audible on-the-air
> > difference in IMD.
>
> I agree, Rich. When running an 8877 at the full 4KV, I have always
> used 12 volts of bias to cut the heat in the shack down a bit. I doubt
> if there is any measurable difference in feculence.
Another thing to remember that any published curves and numbers are
probably averages. The bias "curve" is really a big, fat, wide
"smear." Different tubes of the same type might have bias voltages
that differ by 20% or even a bit more for the same anode current.
I've seen 4cx1600b's that needed 40-60 volts for the same NSAC.
73,
George Daughters, K6GT
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