A large agency like a police department may have numerous talk-groups organized similarly to the channels in a conventional system. In a trunked system, each Road Patrol Unit would typically have its own talk group. Each time a member of a talkgroup starts to transmit, a central computer assigns all members of that talkgroup to an available frequency. All members of this talkgroup will transmit and receive on that frequency for the duration of the conversation.
If a member of a second talkgroup starts to transmit at the same time, the central computer will assign all members of that second talkgroup to the next available frequency. All members of that second talkgroup will transmit and receive on that frequency for the duration of the conversation. When a transmission is over, that frequency again becomes available for the central computer to assign to another talkgroup.
When using a conventional scanner, it is difficult to monitor agencies, including many police departments, that use a trunked radio system instead of a conventional system. Users on a trunked radio system are not given dedicated frequencies. Also, a transmission and its reply may be on different frequencies.
Imagine your frustration at missing the reply in a police chase and instead hearing the dog catcher! In order to fix these problems, manufacturers created "Trunk-tracking" or "Trunking" radio scanners. Trunking scanners use special circuitry that monitors the digital control channel signals that tell talkgroup members which frequency to use.
A trunking scanner can be set to display the number of the talkgroup at any given time, to follow transmissions and their replies within a talkgroup even as the frequency changes, and to only listen for selected talkgroups if one desires.
They have been around since and may now be purchased from a variety of vendors or purchased in used condition through services such as eBay. The Motorola APCO Project 25 system is the only digital system that may be heard on radio scanners, and currently only on a few high-end models see below for more information on digital radio.
Hearing firefighters call for more water pressure as they're inside a building fighting a fire is thrilling. Hearing planes and trains be dispatched and routed is just plain fun. And in all cases you're admiration for the jobs these public servants and private professionals are performing only grows while your knowledge and understanding of their work increases.
You can have a scanner on in the background while you watch TV. Some people even go to bed listening to a scanner at night and, over time, instinctively know and wake up when something exciting or important is happening - you can tell by the tension in the voice of the dispatchers and officers in the street who are communicating.
Particularly for kids, when you're listening to a scanner you're practically riding along in that patrol car or you're in that fire truck racing to a scene of a fire. It's really mesmerizing, entertaining, informative and educational all at the same time.
And, particularly for adults, perhaps those who are concerned about crime in their neighborhood or dry brush around their homes during the fire season, a scanner will keep you abreast of what conditions are in your area. Are police responding to suspicious persons on nearby streets? Do you hear the fire department being called out to hose down homes in the development a few blocks away?
This is invaluable information that you can find nowhere else or not nearly as quickly. A scanner radio does it all. So we hope you'll consider buying yourself or a loved one a scanner today.
For information, for entertainment, for peace-of-mind, and more. There's nothing like a scanner. Distance depends on too many factors to provide an easy answer, such as the elevation of your home, whether there are hills or other obstructions between you and the agency you wish to monitor; the transmitter power of the agency you wish to listen to, etc. These and other factors all play a part. Generally speaking, with a handheld or desktop scanner you can hear in a 10 to 20 mile radius, but that's not set in stone.
What is Trunking? As public safety agencies and businesses grow they require more and more radio frequencies for their operations, consequently available radio spectrum has become more valuable and more difficult to find. To help resolve this problem, radio manufacturers developed trunking which works on the same principle as a trunk telephone line.
Let's take for an example the city of Worcester, Massachusetts. This mid-size city used to have two or three frequencies for the police department and two or three for the fire department as well as one for public works and one for parks. Now, with their trunking radio system, they have upwards of 50 or groups of users on 10 radio frequencies.
Every time a police officer, a firefighter or a sanitation worker presses his microphone button an instantaneous computer command is sent out to all the other users within that person's radio group to move to one of the nine available voice frequencies in the system.
The channel the group is assigned is almost completely random so there's no way to follow a communication unless you have a trunking scanner that works on a principle similar to that of the actual two-way radio. Hence, the TrunkTracker. One moment an officer in the police east side traffic division may be calling his dispatcher on one of the nine frequencies, and seconds later that dispatcher may reply to that officer on a completely different frequency.
So now, a small group of radio users, such as the Water Filtration division, can effectively have their own radio channel. It's not a frequency per se, just any one of the 9 available radio frequencies as long as it's not in use by another talk-group of users.
A popular business trunking technology is known as LTR. Most, but not all, public safety trunking systems operate on the MHz band. As the technology has evolved over time, each manufacturer has some different flavors of their trunking system. Type I requires something called a fleet map to work properly although these systems are gradually being phased out.
See next Question for additional information. Some very Older scanner models, built before , were able to be frequency "modified, or Restored" to hear the older obsolete "analog" cell signals as mentioned above.
If you do get any reception improvement with a new scanner, consider it an "unexpected" bonus! A - "Scan" allows your Radio to run through your preset memory channels, stopping on any channel that is active. Some units do Not have any Search features. A - Yes. See our Shop OnLine Catalog for more info. This new feature allows the radio to Instantly auto tune itself to any nearby Radio transmission, without the need to scan, search or know the frequency! It usually works up to a couple of hundred feet, depending on the transmitter.
Trading your 5 inch "rubber duck" for a different brand 5 inch "rubber duck" probably won't make much difference. Most signals that you will listen to on a Scanner have "Line of Sight" reception qualities. You generally want features such as Freq coverage to Mhz, at least channels and AlphaNumerics for the Best "race" use A - Yes, We've taken care of that!
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