Propagation in the VHF and UHF bands between 30 MHz and 3 GHz takes place in the tropospheric mode. The major use of two-way radio communications in the VHF and UHF bands is communication between a fixed base station and several mobile units located on vehicles, ships, or aircraft in the frequency band 30-470 MHz. Typical applications are in control-tower-to-aircraft communication at airports, fire departments, ship control within harbours, police departments, armed-forces field operations, pipeline and transmission line maintenance, highway maintenance, taxicab and delivery vehicle despatch, and personnel paging systems.

Since these systems operate in frequencies above 30 MHz, their range of operation is limited to within ...

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