Easier to Read BCD996P2/XT Digital Scanner Manual Also the 996P2 ...
Understanding TrunkingContents
Trunking systems let a large group of 2-way radio users (or even different groups of 2-way radio users) efficiently use a set of frequencies. Instead of selecting a specific frequency for a transmission, the user’s radio selects a programmed trunking bank in the system when that user presses their PTT (push to talk) button. The trunking system automatically transmits the call on the first available frequency, and also sends (on a different frequency called a Data or Control channel) a code that uniquely identifies that transmission as a talkgroup ID (or just ID.) So when you are trunktracking a system, you are listening to active IDs transmitting in the system (each using the first available frequency in the system). Trunking systems in general allocate and use fewer frequencies among many different users.
Since the trunking system might send a call and its response on different frequencies, it is difficult to listen to trunked communications using a conventional scanner. These scanners let you monitor the control channel frequency so you can hear calls and responses for users and more easily "follow" conversations than with a conventional scanner.
These trunking scanners trunktrack the following types of systems:
- Motorola Type I
- Motorola Type II
- Motorola Type IIi Hybrid
- Motorola Type II Smartnet
- Motorola Type II Smartzone
- Motorola Type II Smartzone Omnilink
- Motorola Type II VOC
- LTR Standard
- Project 25 Standard
- P25 Phase I and Phase II (996P2 only)
- P25 X2-TDMA (996P2 only)
- EDACS Standard (Wide)
- EDACS Narrowband (Narrow)
- EDACS Networked (Wide/Narrow)
- EDACS SCAT
- EDACS ESK
When you program
Motorola/P25 and EDACS system frequencies into the scanner, one frequency is the control (or data) channel, and the rest are voice frequencies shared by all the users. There may be 3 or 4 frequencies assigned as (primary or alternate) control channels but only one control channel will be active at a time. These scanners will allow you to program just Motorola/P25 control channels into the trunking system and the voice channels will automatically be found (but not programmed). EDACS systems need all the frequencies for the system programmed
and in the correct
LCN (Logical Channel Number) order.
The control channel is continually transmitted to the field units and has a sound similar to listening to a boat engine over the phone (in manual mode; you won't hear this when you are trunking the system.) This control channel is also a good check to see if you can trunktrack the system. If you
can't hear a control channel when you step through the trunking frequencies (in manual mode), you either don't have all the frequencies or are too far away to receive the control channel and the system. Motorola systems are limited to a maximum of 28 frequencies per system or site. Ericsson EDACS systems are limited to 25 frequencies per system or site. Motorola and EDACS systems can be either analog, digital, or mixed (digital and analog talkgroups). Mixed Motorola systems should be programmed as Motorola systems and not P25 digital systems. That way the talkgroup options will allow you to select if it is a digital or analog.
LTR systems work a little differently. LTR systems typically do not have a dedicated control channel. This type of system encodes all trunking information as digital subaudible data that accompanies each transmission. The frequencies also have to be in
LCN (Logical Channel Number) order or the correct 'slot' for the system to trunktrack properly. Each repeater has its own controller, and all of these controllers are synchronized together. Even though each controller monitors its own channel, one of the channel controllers is assigned to be a master that all controllers report to. Each of these controllers sends out a data burst approximately every 10 seconds so that the subscriber units know that the system is there. This data burst is not sent at the same time by all the channels, but happens randomly throughout all the system channels. If you listen to the frequencies of an LTR system in manual mode (not trunking), on every channel in the system you will hear this data burst that will sound like a short blip of static like someone keyed up and unkeyed a radio within about 500 msec. LTR systems are limited to 20 frequencies per system.
Trunkscanning is basically scanning IDs that are programmed into ID locations (same concept as frequencies into channels). You can then trunkscan just the programmed IDs.
Trunktracking is searching for
all IDs in a system (same concept as searching for frequencies in a band).
Some Motorola and EDACS systems covering a very large geographic area use multiple antenna sites that each operate on different frequencies and use the same talkgroup IDs for traffic. Each site will have its own set of trunking frequencies and is monitored like a single system. Each site can have its own quick key, so you can turn each individual site on or off while you scan. Program your talkgroups into channel groups within that system and all talkgroups in the system are available to every site so they don't have to be reprogrammed for each site. Since all sites share all the talkgroups within the system, multi-site trunking is much more efficient than programming each site as a separate system.
Radio Reference.com has an excellent page explaining the various types of trunking systems in more detail
here.
Understanding IDsContents
IDs are what you see instead of frequencies when you monitor a trunking system.
Motorola IDs come in two display formats: Type I and Type II. Each format displays and uses talk group IDs in slightly different ways. Type I/II hybrid systems use both fleet-subfleet and 5-digit formats for talk group IDs.
Type I IDs are in the format
FFF-SS where
FFF is the fleet and
SS is the sub-fleet. Type I systems are usually organized with different IDs assigned to different fleets. For example, a valid fleet/subfleet ID identifying all detectives within a police department might be 000-12, where 000 identifies all police IDs and 12 identifies the Detective division. To properly trunk a Type I system, you have to program the fleet map for the system.
Type II IDs are identified by a 5-digit number.
EDACS IDs come in two display formats:
AFS and
Decimal.
AFS IDs are in the form
AA-FFS where
AA is the agency,
FF is the fleet, and
S is the sub-fleet. EDACS systems are organized with different IDs assigned to different fleets and agencies. For example, a valid agency/fleet/subfleet ID identifying all detectives within a police department in an agency might be 06-101, where 06 identifies the agency (Police), 10 identifies the Police division (East side), and 1 identifies the Detective division.
Decimal IDs are shown as a decimal number from
0 to
2047.
You can find a chart showing Decimal and AFS IDs here:
Conversion Chart.
I-Call IDS (Motorola/EDACS only) are direct unit-to-unit transmissions that are not heard by other system users. I-call IDs are usually 6-digit IDs (ex: 700152).
Unit IDS (or Radio IDs) are 7 or 8 digit numbers identifying individual radios.
Note: To view unit IDs you have to turn the option on in the '
Settings' menu.
LTR IDS are in the format
A-HH-UUU where
A is the area code (0 or 1),
HH is the home repeater (01-20), and
UUU is the user ID (000-254).
(Get ProSCAN software as its best for this, or use FreeScan, but be aware FreeScan is no longer being supported and was discontinued.)
