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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