..~wa5bxo/asyam/Amplitude%20Modulation.htm
The television visual carrier is amplitude modulated in such a
way. The black parts of the picture, in which noise is most
easily seen, are transmitted at the highest power, and the white
portions are transmitted at the lowest power.
Likewise the top peaks of the audio voice waveform do not
contribute as much to inteligibility, but the bottom sections do,
and so he has inverted the signal to place the part which is both
more important and more succeptible to obfuscation by noise in a
position such that it is transmitted at the higher power level.
The higher carrier and higher average power is a byproduct of this.
PJ
