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http://en.wikipedia.org/wiki/Amateur_radio_station
Mobile stations
An amateur mobile radio station.
An amateur radio station installed in a vehicle is referred to as a mobile station. A typical mobile station is equipped with a transceiver, one or more antennas, and a microphone. The transceiver may be specially designed for installation in vehicles. It may be much smaller than transceivers designed for fixed station use, to facilitate installation under a seat or in a trunk, and it may feature a detachable control head that can be mounted in a separate location from the rest of the radio. Antennas designed for mobile stations must accommodate the unique physical constraints of the vehicle and travel lanes which it occupies, allowing for clearance under overpasses and bridges, and safe passage by vehicles in adjacent lanes. Most antennas used in mobile stations are omnidirectional. Few mobile stations are equipped to communicate with Morse code or digital modes. Most mobile stations are designed to be operated by the vehicle operator while driving.
Most transceivers installed in vehicles are designed to run on 12-16 VDC, and are generally powered by the starting battery in the vehicle. Because of the power demands placed on the vehicle battery, most mobile stations either do not include external amplifiers or include amplifiers with power outputs that are more modest than those commonly found in fixed stations.
A specialized form of mobile station used for competition in a VHF amateur radio contest in North America is called a rover station. A rover station is often designed to be operated by a passenger in the vehicle rather than the driver, and may include multiple transceivers, transverters, directional antennas, and a laptop computer to log contacts made.
While it may not be a regulatory requirement, many mobile stations will append a /M to end of their call sign (pronounced as "slash mobile" on phone) while operating to identify themselves to other stations as a mobile station. Rover station operating in a VHF contest will append a /R to the end of their call sign (pronounced "slash rover").
Maritime mobile stations are mobile stations installed in a watercraft, usually an ocean-going vessel. When in international waters, these stations are operated under the regulatory authority of the flag under which the vessel is registered. In addition to the regulatory requirements of amateur radio, operation of maritime mobile stations also requires the permission of the captain of the vessel. Maritime mobile stations append a /MM to end of their call sign (pronounced as "slash maritime mobile").
Aeronautical mobile stations are mobile stations installed in an aircraft. In addition to the regulatory requirements of amateur radio, operation of aeronautical mobile stations also requires the permission of the pilot of the aircraft. Aeronautical mobile stations append a /AM to end of their call sign (pronounced as "slash aeronautical mobile").