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Police radio systems historically used public radio frequencies, and listening to them was, for the most part, legal. Most modern police radio systems switched to encrypted radio systems in the 1990s and 2000s to prevent eavesdroppers from listening in.
A radio band is a small frequency band (a contiguous section of the range of the radio spectrum) in which channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands.
In the Americas (defined as International Telecommunication Union (ITU) region 2), the FM broadcast band consists of 101 channels, each 200 kHz wide, in the frequency range from 87.8 to 108.0 MHz, with "center frequencies" running from 87.9 MHz to 107.9 MHz. For most purposes an FM station is associated with its center frequency.
Shortwave bands are frequency allocations for use within the shortwave radio spectrum (the upper medium frequency [MF] band and all of the high frequency [HF] band). Radio waves in these frequency ranges can be used for very long distance (transcontinental) communication because they can reflect off layers of charged particles in the ionosphere and return to Earth beyond the horizon, a ...
Frequency allocation (or spectrum allocation) is the part of spectrum management dealing with the designation and regulation of the electromagnetic spectrum into frequency bands, normally done by governments in most countries. [1] Because radio propagation does not stop at national boundaries, governments have sought to harmonise the allocation ...
In addition to radio frequencies used to connect handsets with cellular base stations, other parts of the radio spectrum are used to interconnect base stations and the wired telephone network. Some frequency bands may be vulnerable to interference by existing services in adjacent frequency bands, such as UHF television broadcasting.
Radio users will confine all radio transmissions to an emergency in progress or a new incident. Radio traffic which includes status information such as responding, reports on conditions, at scene and available will not be authorized during this period. Emergency Traffic Term used to gain control of radio frequency to report an emergency.
Adjacent frequencies are often used by illegal operators using modified CB or amateur radio equipment. Operators sometimes refer to this activity as freebanding. The Industrial/Business Radio Pool of the Private Land Mobile Radio Services has several channels just above the Citizen's Band, at 27.430, 27.450, 27.470, 27.490, 27.510, and 27.530 MHz.