The documentation part is done. Check out the
textbooks and articles written over the years by W1FR,
Fritz (aka Frederick) Raab. He has built and
documented an envelope removal and restoration high
efficiency amplifier which he has, indeed, operated on
the ham bands. Fred's work would be system-level,
encompassing the interplay of the RF portions,
modulated power supplies, amplitude and phase feedback
systems, requisite filtering, etc. Fred used to run a
company called Green Mountain Radio Research, but I do
not know if that is still the case.
For extremely detailed discussions and theories of the
Class D, E, etc, portions of the RF deck, look for
writings by Nate Sokal (WA1HQC).
Neither gentleman tends to use his callsign with his
works, so it is prudent to limit your searches to name
only. Any of the trade magazine website, plus the
usual tech book publishing houses (Artech,
Prentice-Hall, etc) are reasonable places to search
for the works of these two gentlemen.
A web site sounds like a fine idea. I should like to
do just such a thing, when it is notably higher on my
priority list.
73,
Dave W8NF
--- "R. Measures" <r@somis.org> wrote:
> ** Dave -- Why not design a 90% efficient linear
> amplifier for the HF
> Ham bands, document the construction process, and
> show us how to on your
> Web site.
>
> >In the late 1980s, one of the engineers I worked
> with
> >had recently come from Continental Electronics of
> >Dallas, TX. The most recent transmitter design on
> >which he had worked at Continental was a
> multi-hundred
> >kW rig. It used a solid-state switchmode
> plate/screen
> >modulation, with loop feedback to keep the
> distortion
> >low. The transmitter was capable of operation from
> AM
> >BC (not legal in the US at that power level) to in
> >excess of 20MHz. Because of the custom nature of
> such
> >large transmitters, it was, of course, not
> >band-switched. Rather, the purchaser specified the
> >operating frequency.
> >
> >However, the techniques, without question, could
> lend
> >themselves to a band-switched design. And there's
> >nothing preventing such techniques when the RF
> devices
> >are solid state.
> >
> >There is nothing inherent in a high efficiency
> >broadcast design that renders it narrowband.
> >
> >Complex? Yes. Technically difficult? No.
> >
> >73,
> >
> >Dave W8NF
> >
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