Re: [Amps] Plate modulator xmfr ?

[Bill Fuqua <wlfuqu00@uky.edu>]

What formulas would you use?
By the way, one reason to modulate the screen grid along with the plate is 
to make the
tetrode tubes' plate impedance appear to be more like a triode than a 
tetrode. The plate current
increases with applied plate voltage. So that the power output is 
proportional to the square
of the applied plate voltage and the plate resistance as seen by the 
modulator appears to
be fairly constant. Naturally it all goes to heck when the modulated plate 
voltage becomes very low.
But that is the point that you should never reach unless you intend to 
over-modulate.

73
Bill wa4lav



the screen dissipation when the modulated plate voltage is low.

At 10:26 AM 10/10/2004 -0700, you wrote:

> On Oct 10, 2004, at 7:45 AM, Vic Rosenthal wrote:
>
> > StephenTetorka@cs.com wrote:
> > > Hi all:
> > > I need to better understand the workings of a plate modulator for AM.
> > > Considering the RF amp with 2 x 813's and the modulator with 2 x 813's - 
> > > what are the equations and math to work out the required wattage, 
> > > impedance, step ratio etc.
> >
> > What I suggest is that you get a copy of the ARRL handbook from the early 
> > 50's or late '40's.  In addition to the information you seek, you'll find 
> > lots of stuff about methods of improving the effectiveness of the system 
> > (clipping & filtering, overmodulation prevention, etc.) as well as 
> > practical examples of circuits.  You might avoid some mistakes.
>
> Using the modulation formulas in these publications is a mistake.
>
> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>
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