[AMRadio] origin of Class B


Mike Sawyer w3slk at uplink.net
Thu Feb 16 17:10:09 EST 2006


Thanks, John.
    I guess the old adage holds true: don't believe everything you hear and 
only half what you see (or read). The book framed it that Collins was 
actually responsible for class B high level modulation. I'll go back a 
re-read that part just to make sure I didn't miss anything.
Mod-U-Lator,
Mike(y)
W3SLK
----- Original Message ----- 
From: "John Lyles" <jtml at losalamos.com>
To: <amradio at mailman.qth.net>
Sent: Thursday, February 16, 2006 5:00 PM
Subject: [AMRadio] origin of Class B


Loy Barton of RCA wrote one of the first class B high power audio amplifier 
reports. He developed the concept of plate modulation with a high level push 
pull audio driver for his thesis at Univ of Arkansas radio station. You can 
read the report from 1930 here:

http://www.amwindow.org/tech/htm/tutor.htm

I summarized the events which led to Barton's paper in QST in 1931, followed 
by Art Collins paper in 1935 on the benefits of this approach.

http://www.amwindow.org/tech/htm/heisingorwhat.htm

73
John
K5PRO


> Message: 4
> Date: Wed, 15 Feb 2006 18:48:52 -0500
> From: "Mike Sawyer" <w3slk at uplink.net>
> Subject: Re: [AMRadio] AM Transmitter Advice??
> To: "Discussion of AM Radio" <amradio at mailman.qth.net>
>
> Don, K4KYV said: Sometime in the late 1920's, it occurred to someone that
> class-B linear
> amplification would work just as well for audio as for rf, and the class-B
> audio amplifier was developed.  The unusual thing about this setup was the
> large audio transformer required.  Many rf linears were single-ended, and
> depended on the fiywheel effect of the rf tank circuit to supply the 
> missing
> half of the sinewave output.  With class-B audio amplification, the tubes
> have to be in pushpull in order to reproduce both halves of the sinewave.
> Thus the well-known "class B modulator" came into being.
>
> Interesting that you mention this Don. I just read where it was Art 
> Collins
> and his group that came up with the idea of using Class B push-pull audio
> for Class C rf amplifier. I'm not a Collins aficionado but Joe, N3IBX gave
> me the book, "The First Fifty Years of Collins" to read and I found it 
> very
> good reading. There was some self-promoting in there but I was mildly
> surprised when I learned Collins did discover the Class B P-P plate
> modulation scheme.
> Mod-U-Lator,
> Mike(y)
> W3SLK
>
>
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