Ampitude Modulation (AM)

A method of transmitting information by varying the strength (amplitude) of a carrier wave in proportion to the signal being sent.

Amplitude Modulation (AM) is a technique used in marine radio communications to encode audio or data signals onto a carrier wave by altering its amplitude. The frequency of the carrier remains constant, but the amplitude changes in response to the input signal, such as voice or other audio. This allows the signal to be transmitted over long distances and received by compatible radio receivers tuned to the same frequency. AM is commonly used in medium frequency (MF) and high frequency (HF) marine bands, particularly for long-range voice communication and distress signals, such as those on 2182 kHz. While AM is more susceptible to noise and interference compared to frequency modulation (FM), it remains important in maritime operations due to its simplicity and ability to travel great distances, especially over water where signal propagation is enhanced. AM signals can be demodulated using relatively simple equipment, which contributes to their continued use in both commercial and recreational marine radio systems.