Linear amplifiers are not new to radio. They were used in the thirties -
yes to amplify am transmitters. It is old technology, and perfectly proper
to put out a signal that way.

When you compare efficiencies of a linear amplifier to a full blown class C
plate modulated amplifier, you must consider the filament and plate power of
the modulator.

I worked a number of stations in the fifties that were running a low level
transmitter into a linear amplifier, and they sounded excellent. The
Central Electronics 100V and their linear amplifier put out an excellent AM
signal. Even the KWS-1, which transmitted AM using only one sideband,
sounded great.

The modern amp covers 160, though, along with the other bands, so of one is
lazy (hence his name), the linear is a reasonable approach.

Colin K7FM