When tracking these types of systems, you might want to remember that your scanner can track more than one trunking system at a time and scan conventional and trunked systems at the same time.
Conventional scanning is a simple concept. You enter a frequency used by someone you want to monitor into your scanner’s memory. For example, the police in your area might transmit on 460.500 MHz, the fire department on 154.445 MHz, the highway department on 37.900 MHz, etc. So 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. This type of scanning is easy and fun.
However, as the demand for public communications has increased, many public radio users do not have enough frequencies to meet their needs, creating a serious problem. Trunking radio systems help solve this problem.
Trunked Scanning
While conventional scanning worked great while there were only a few groups wanting to use the frequencies, with the advent of smaller,
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
21 | Understanding Scanning |
