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The first police radio systems were implemented in Detroit in 1928, when the Detroit Police Department set up a one-way radio system to broadcast crime information to police cars. [2] The frequency was assigned the call sign "KOP" by the Federal Communications Commission .
Radar-frequency bands according to IEEE standard [17] Band designation Frequency range Explanation of meaning of letters; HF: 0.003 to 0.03 GHz: High frequency [18] VHF: 0.03 to 0.3 GHz: Very high frequency [18] UHF: 0.3 to 1 GHz: Ultra-high frequency [18] L: 1 to 2 GHz: Long wave S: 2 to 4 GHz: Short wave C: 4 to 8 GHz: Compromise between S ...
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 ...
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.
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In addition to showing an incorrect frequency, there are two other disadvantages that can result in undesired performance; the converter cannot down-convert in full the regular international FM band (up to 20.5 MHz wide) to the only 14 MHz-wide Japanese band (unless the converter incorporates two user-switchable down-convert modes), and the car ...
Hopper had been involved in radio for years and realized there was a need to abbreviate transmissions on State Police bands. [6] Experienced radio operators knew the first syllable of a transmission was frequently not understood because of quirks in early electronics technology.