Uniden UBCD396XT Radio Systems Overview, Conventional radio systems, Trunked radio systems

UBCD396XT

17.Radio Systems Overview

There are two basic types of radio systems: conventional systems and trunked systems.

Conventional radio systems

In a conventional radio system, each group of users is assigned one (for simplex systems) or two frequencies (for repeater systems). For example, the police in your area might operate on 460.500 MHz, the fire department on 154.445 MHz, the highway department on 37.900 MHz, etc. All transmissions from each group always go out on the on the same frequency--the police won't randomly switch to 500.000 MHz, for instance.

Since each group always stays on the same frequency and frequencies never overlap, it's very easy to follow conversations on conventional systems: when your scanner stops on a frequency, you usually know who it is, and more importantly, you can stop on a channel and listen to an entire conversation.

Up until the late 1980s, this was the primary way that radio systems operated. Some examples of conventional radio systems are

∙Aircraft

∙Amateur radio

∙AM CB/UHF CB users

∙Small, private radio systems

Trunked radio systems

Several major trends have converged that have resulted in agencies moving to more efficient trunked radio systems:

∙Higher levels of radio usage has meant that there aren’t enough individual frequencies available to allow every group to have their own frequency.

∙Technology advances have brought down the overall cost and complexity of implementing a trunked radio system while increasing the features available to the agency and individual radio users.

∙Roll-out of major statewide trunked systems makes it easier for even small agencies to piggy back onto the larger system for less cost than replacing existing systems.

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