[Amps] Transistor amps

[Vic Rosenthal]

Dr. William J. Schmidt, II wrote:

> Check these out... I just uploaded them to my website.  They make fine CW 
> amps... need a little work for SSB... but not much!
> 
> http://www.wjschmidt.com/ham/apt9502.pdf
> 
> http://www.wjschmidt.com/ham/apt9701.pdf

The notes don't discuss protective circuitry, if needed.  You might want to 
protect it from high SWR, overdrive, high temperature, and overcurrent.

Every time I talk to anyone 'in the business' about producing amateur amplifiers 
of this type, they say that the price point for a 1.5 KW amp would be over $3K, 
by the time you add the power supply, protection, filter, autotuner, control 
circuits, etc.  As a homebrew project, it's not too easy  because of the lack of 
a complete, tested design and the need to make a PCB.

I believe that a 'people's amplifier' could be developed using the APT MOSFETs 
that would incorporate the power supply, protection, biasing, and filtering 
that's needed for a practical unit that could be built by a reasonably careful 
ham for less than $1K.  By using relay-switched filters, the amplifier could be 
entirely no-tune.

Although I think the inherent linearity of these transistors is not that great, 
possibly some kind of negative feedback could be employed to improve it (I'm a 
CW operator and would be happy with class C, but I understand that others have 
different needs).

Who needs an Alpha 87 at $6K when this is possible?

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco