DMA Scanners and Trunking
What is Trunking?
Trunking involves the use of many agencies, sharing a specific set of frequencies. Each agency - or sometimes more than one - are allocated logical addresses referred to as a Talkgroup. If you are new to this topic, stick to the Overview section for now. Bookmark this article and come back to it later if you wish to learn more details.
How Can I Determine Whether a Model Will Trunk My System?
Each scanner's article has a section entitled RR System Compatibility. This section is designed to mimic, as closely as possible, the listings of system types and voice as found on the database. In general, if your system type or voice is not listed in this section, chances are the scanner will not be able to decode it.
The following summarizes each of the DMA scanners, and types of trunking they will handle;
What Formats Cannot be Trunked?
Some of the most common formats include:
How do I Find Out What Systems exist in my Area?
RadioReference has an extensive and searchable database for many areas of the country. All you need to know to use it is your state, county and sometimes the city of interest. Look in the upper left tab for 'Trunking'. This lists all the trunking systems in the database for your area.
I am having trouble receiving TGs above 4096
- Early versions of the firmware for the non-XT scanners had these issues. They have since been solved by firmware updates.
Trunked audio chops out / stops after a couple seconds
- Most of the time, this is caused by the incorrect setting of the system type. While the various software packages implement the necessary variables a little differently, these 3 rules can generally be applied to the entries found in the RadioReference database;
1. If the System Type says Project 25 Standard and the System Voice says APCO-25 Common Air Interface Exclusive then the system type should be programmed as P25. Only the BCD396T, BCD996T, BCD396XT and BCD996XT will handle these systems. Be sure to set the APCO Mode to Auto, and supply a threshold for decoding. An example of this type of system can be found here
2. If the System Type says Motorola Type II SmartZone and the System Voice says Analog and APCO-25 Common Air Interface, program this system as a Motorola Type 2. Set the APCO mode to Auto, and supply a threshold for decoding. Systems like these are often referred to as a mixed mode, Project 16 or P16 system. An example of this type of system can be found here. Note that only the BCD396T, BCD996T, BCD396XT and BCD996XT will handle the digital talkgroups found in such a system.
3. If the System Type says Motorola Type II (any variant) and the System Voice says Analog this is neither a P25 nor a mixed mode system. Program this system as a Motorola Type 2. The APCO mode and threshold should be ignored. An example of this type of system can be found here
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