A 'perfect' 100% modulated AM transmission carrying a sinewave should have
4.8 dB peak to mean, so what mechanism can account for 6.9dB ? This
certainly does seem to reinforce the idea that the carrier reduces with
amplitude.
Here in the U.S., positive peak levels of 125% are allowed. The maximum
negative peak level is obviously 100%, the point at which the carrier goes
away. Not sure what the regulations are over there, but the asymmetry might
explain the readings.
And I'll echo some earlier comments, here. I used to be in charge of a 5 kW
PDM rig that had very little carrier shift with "old fashioned" audio
processing ahead of it. But with an Optimod, it used to buck quite a bit. No
amount of twiddling with the tilt or other settings on the Optimod would get
rid of it.
John Andrews, W1TAG
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