Uniden UBCD996T Owner's Manual download pdf (Page 25)

Trunked Scanning

Types of Trunking Systems

While conventional scanning worked great while there were only a few groups

wanting to use the frequencies, with the advent of smaller, lower-cost radios more

and more agencies and businesses wanted to take advantage of the utility of 2-way

radio. As a result, the bands that were used most became full, so new users were

not able to take advantage of the technology as quickly as they wanted.

Trunking solved this frequency shortage by allowing multiple groups to use the same

set of frequencies in a very efficient way. While each type of trunking system

operates a little differently (see the next few sections), they all work on the same

basic premise: even in a system with a lot of users, only a few users are ever

transmitting at any one time.

Instead of being assigned a frequency, as with conventional systems, each group is

assigned a talk group ID. A central computer controls the frequency each group

operates on. This frequency selection is made each time a user transmits. So, while

on a conventional system queries, replies, and follow-ups are all on a single

frequency, they could each be on completely different frequencies on a trunked

system. This semi-random frequency assignment made monitoring such a system

impossible prior to Uniden’s invention of the TrunkTracker scanner.

Not only does your UBCD996T scan channels like a conventional scanner, it actually

follows the users of a trunked radio system. Once you know and program a talk

group’s ID (TGID), you won’t miss any of the action.

If you are a new scanner enthusiast, you might want to read the first part of this

manual and use your scanner in conventional mode before you begin trunk tracking.

Understanding scanning fundamentals and terminology will make trunk tracking

much easier. If you are already an experienced scanner operator, you can review

the programming worksheets and their associated pages in the Reference Section

of this manual.

Trunking systems divide a few frequencies among many different users, but the way

that each system does this is slightly different. This section describes some of the

technical data behind Motorola, EDACS, and LTR trunked radio systems.

While there are different types of Motorola trunking systems, they all use the same

basic trunking method. The system consists of one control channel (or as many as 4

per system but only one is active at any one time), plus one or more voice channels

(typically 10, 20, or 28 total channels). When a user presses Push To Talk (PTT) to

transmit, their radio first sends the person’s talk group information to the control

channel. The computer then assigns that talk group to a specific voice channel and

transmits that data over the control channel. All radios in that talk group switch over

Motorola Trunking

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Uniden UBCD996T Owner's Manual Page 25