History Mobile radio
in 1970s, california department of forestry requirement 6-frequency transmit, 3-frequency receive, scanning, , 5-tone burst encoder unusual, leading custom-built mobile radio.
solid state equipment arrived in 1960s, more efficient circuitry , smaller size. channel spacing narrowed 20–30 khz modulation deviation dropping plus-or-minus 5 kilohertz. done allow more radio spectrum availability accommodate rapidly growing national group of two-way radio users. mid 1970s, tube-type transmitter power amplifiers had been replaced high-power transistors. 1960s 1980s, large system users specialized requirements had custom built radios designed unique systems. systems multiple-ctcss tone encoders , more 2 channels unusual. manufacturers of mobile radios built customized equipment large radio fleets such california department of forestry , california highway patrol.
examples of hybrid partially solid state mobile radios:
motorola motrac
motorola mj imts car telephone (1963)
general electric transistorized progress line
general electric mastr professional , mastr executive
rca super carfone
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