FBI Radio Teardown (Motorola Spectra)

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1. Thanks for many educational video. I saw your wilkinson slitter video, it was very good learning to me, I do understand how they work now, thanks to you. I will watch more video of yours in future.

   Japan is probably one of the first country in the world , where police radio went digital in early 1980’s. Japanese have nationalized frequency sets just allocated for police. This is something like CB radio with many frequency set. This way there is only one type of radio necessary to cover entire country. And useful when one region of police car go to different region , they just have to switch the channel. ( sort of like 700 MHz APCO system in US ) The frequency is 150 MHz band for vehicle mounted or portable radio, 350MHz for handheld units for short distance communications. Since 1980’s They have changed their digital format several times. and current digital radio are simulcast radio , so there are multiple transmitter transmit on same frequency to cover wider area and eliminate dead spot. They use TDMA access, so Vehicle Mounted radio can be used as temporary repeater, in case of poor radio coverage in rural area. This is done by using one time slot to receive , and next time slot to re-transmit. Digital Radio also transmit some low speed data such as GPS location so on. Because of Simulcast, they use less frequency compare to older analog narrow band system, where they needed many different frequencies pairs for different repeaters to cover different area. Japanese TV broadcast system also use low symbol rate OFDM simulcast system. so they have many transmitter cover certain region with one frequency. With Analog NTSC signal, each frequency channel in UHF was need to cover dead zone. Japan has many hills and mountain, so simulcast is very useful.