Disadvantages
Because of the extremely high rotational speed compared to a conventional alternator, the Alexanderson alternator required continuous maintenance by skilled personnel. Efficient lubrication and oil or water cooling was essential for reliability, difficult to achieve with the lubricants available at the time. In fact early editions of the British Navy's "Admiralty Handbook of Wireless Telegraphy" cover this in considerable detail, mostly as an explanation as to why "The Navy" did not use that particular technology. However, in the US Navy it was.
Other major problems were that changing the operating frequency was a lengthy and complicated process, and unlike a spark transmitter, the carrier signal could not be switched on and off at will. The latter problem greatly complicated "listening through" (that is, stopping the transmission to listen for any answer). There was also the risk that it would allow enemy vessels to detect the presence of the ship.
Because of the limits of the number of poles and rotational speed of a machine, the Alexanderson alternator is at most capable of transmission in the lower mediumwave band, with shortwave and upper bands being physically impossible.
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