"Reg Edwards" wrote in message ...
According to Fourier, at some mark-space ratios of a square wave certain
harmonics may be missing from the spectrum.

Just generate a a train of very short sharp pulses from the oscillator and
you will find all the harmonics are present allbeit with reducing
amplitudes. A single transistor should do the job.

The inverse of the duty cycle. For a square wave 1:1 M/S = 1/2 duty
and all harmonics divisble by 2 are absent. For duty 1/5, fifth
harmonic (and multiples)are absent.