[AMRadio] Re: Screen Modulated 813


Bry Carling bcarling at cfl.rr.com
Mon Dec 11 16:09:57 EST 2006


Lary - I was talking about the kind of set-up with the 6DE7 
that produces a SMALL carrier of say 6 or 8 watts
and then does 90 watts p.e.p. on the voice peaks.

I may be nuts, but my empirical sense tells me that is 
far more impressive sounding in the receiver n the other 
end than the signal from the typical "novice rig" that runs
75 watts carrier input with Heising mod. OR even a plate 
modulated class C rig with 22.5 watts carrier input and 
90 watts p.e.p.

The power is turned DOWN during the inefficient phase 
of the transmission in other words.

WIth less and less quiescent signal the transmitter appraoches 
the efficiency level of a DSB rig.

> Bry Carling writes:
> > 
> > DX-60 followed by an 813 RF linear or SB200. 
> > 
> > Versus: 
> > 
> > 813 screen modulated final using the same method that sets 
> > the quiescent carrier level at about 10% of peak signal. 
> > 
> > Which would be more efficient?  
> > 
> 
> It's my understanding that from a 1st order analysis (ignoring  subtleties 
> like what plate voltage they are being run at, any differences in 
> efficiencies between the tube types, output network design, etc, etc.), the 
> plate efficiencies would theoretically be the same between a 
> screen-modulated stage and a class AB linear amplifier stage amplifying an 
> AM signal, since they are both essentially "efficiency modulation" 
> techniques. 
> 
> 73.0000,
>  -Larry/NE1S
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