BasicB-001-019-006
What is the maximum percentage of modulation permitted for amateur radio voice communications?
B
Answer
Regulations and administration
Type
A
90%
B
100%
C
75%
D
50%
Answer Notes
In voice communications, particularly amplitude modulation (AM) and its derivatives, modulating the carrier wave up to 100% provides the maximum possible clean audio signal. This is the absolute legal and technical limit.
Exceeding 100% modulation is known as overmodulation. Overmodulation causes severe distortion of the transmitted voice and generates unwanted spurious emissions called 'splatter.' This splatter unnecessarily widens your signal and interferes with other operators on adjacent frequencies.
Regulations cap modulation at exactly 100% to ensure the efficient use of the spectrum and to maintain clear, interference-free communications for everyone.
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