"Cecil Moore" wrote:
The question seems to be: If an FM transmitter's output signal
is not a reasonably pure sine wave, is a low-pass filter used
between the transmitter and antenna to reduce the harmonics?
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Yes. This question was answered in my post in this thread of 00:24UTC
today, which I will paste below:

"Harmonics are present at the PA output of an FM transmitter, but "clipping"
is not the process whereby they are generated, as I state above. They are
reduced to legal values using a lowpass/harmonic filter. The FCC
attenuation spec for harmonics and spurs more than 600kHz from Fc is 80dB
below the unmodulated carrier.

The lowpass/harmonic filter does not improve efficiency--it has a small
amount of insertion loss in the FM band."

RF