Overmodulation

1. The condition that prevails when the instantaneous level of the modulating signal exceeds the value necessary to produce 100% modulation of the carrier.

Note 1: Overmodulation results in spurious emissions by the modulated carrier, and distortion of the recovered modulating signal.

Note 2: Overmodulation in the sense of this definition is almost always considered a fault condition.

2. The condition that prevails when the mean level of the modulating signal is such that peaks in the modulating signal exceed the value necessary to produce 100% modulation of the carrier.

Note: Overmodulation in the sense of this definition, if not excessive, is sometimes considered permissible.

Source: from Federal Standard 1037C and from MIL-STD-188