Doherty Amplifier

[Bob Bruhns]

Hi Andre,

I don't know if anyone sold a Taylor system transmitter.  The Taylor system was almost a "lost ark" in the AM community - people
kept asking about it, but the knowledge was lost, until someone gave me the right hint, and I found that patent.

There is a series-modulator system that is basically similar, but it does the trick at baseband, and provides modulated B+ to a
regular Class-C modulated stage.  You would think that this would have been used back in the old days, but the references I see are
recent.  One series device, a tube or a transistor, provides B+ from a supply that is a little higher than the unmodulated B+ level.
This device normally operates just below saturation, and it works as a series element that can reduce the voltage from there.  With
no modulation, it drops the voltage just a little bit to the unmodulated B+ level,  and this device handles the negative modulation
peaks.

A second device goes to a higher voltage supply, about 2.5 the unmodulated B+ level, or a litle higher.  This device is running
almost cut off.  When it is driven into conduction, it can raise the modulated B+ to 2X the unmodulated level or a bit higher.  This
device handles the positive peaks.

Efficiency is reasonably high at carrier level, dropping somewhat with modulation, but no big audio transformers or inductors are
required, and no special multi-tapped RF section is required either.  I have seen this system called a 'class-B series modulator'.
It is sometimes used for AM using transistors operating around the 50V level, to modulate solid-state class E RF amplifiers.

www.amfone.net/21stAM/class_b_series.htm

   Bob, WA3WDR


----- Original Message ----- 
From: "Andre Kesteloot" <andre.kesteloot at verizon.net>
To: "Bob Bruhns" <bbruhns at erols.com>
Cc: "AMRAD Tacos" <tacos at amrad.org>
Sent: Wednesday, August 08, 2007 10:31 PM
Subject: Re: Doherty Amplifier




Bob Bruhns wrote:
> An interesting alternative is the Taylor linear amplifier.
>
Bob
thanks for the pointer
do you know who, if anyone, marketed this invention ?
73
André N4ICK
>
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