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Amplitude modulation (AM) is one of the modes frequently used by pirates on HF and mediumwave. Often, pirates will use vintage amateur radio transmitters, such as those by E.F. Johnson (Valiant, Viking, Ranger), Globe and Heathkit. These transmitters are old, heavy and consume generous amounts of electricity, but are desirable because they can produce a relatively high fidelity, plate-modulated AM signal. At one time, these transmitters hardly had any value, but prices of vintage equipment have skyrocketed in the last decade. This may be one reason why AM is not quite as popular for pirate transmissions as it once was. Instead, many pirates prefer to use SSB.