Richard Fry wrote:
"Note that without adjustment, modern solid-state FM broadcast
transmitters can (and do) provide 80% or better PA efficiency into a 50
ohm load across 20% bandwidth, with no tank circuit or other in-band
filter(s)."

Well, Richard Fry didn`t say there were no out-of-band filters or traps.

One could have a low-pass filter that cut-off above 108 MHz, but below
176 MHz, and no harmonic would get through the filter.

80% or better efficiency isn`t coming from a Class A amplifier, so maybe
it comes from a Class B amplifier.

One fly in the ointment is found on page 354 of Terman`s 1955 edition:
"The theoretical maximum possible plate efficiency that can be realized
in a Class B amplifier is pi/4 or 78.5 per cent;---."

Best regards, Richard Harrison, KB5WZI