Doherty Amplifier

[Frank Gentges]

I opened my latest copy of RF Design magazine and found an article about 
a Doherty amplifier for 900 MHz.  This is a good magazine to get and if 
you can qualify, it is free.

There were some very fine Doherty transmitters for AM broadcast that 
generated 50 kW 24/7.  This is a touchy design to get tuned up but once 
done, it is very good at amplifying high peak to average ratio signals 
and did not require the high power audio modulator.

The article can be found at

http://rfdesign.com/microwave_millimeter_tech/Amplifiers/706RFDF4.pdf

George Lemaster can add a lot of info and history of their use with AM 
broadcast.  As I recall, at least RCA used the design and I think one of 
these was installed at WTOP in Wheaton MD.

Frank K0BRA