From: Larry Van Horn [larry@grove-ent.com]
Sent: Thursday, June 03, 2004 10:08 AM
To:
SCAN-L@LISTSERV.UARK.EDU
Cc:
trunkcom@mailman.qth.net
Subject: [TrunkCom] How does New Uniden "Dynamically Allocated
Channels"work?
I thought you folks might enjoy and appreciate this explanation on how the new Uniden Dynamic Memory Mamnagement feature works on their new scanners being released this year.
Traditional scanners all worked using predefined banks of channels. Essentially, the total number of channels available were divided by 10, and assigned to the 10 banks. So, a 300 channel had 10 banks of 30 channels each. A 1000 channel scanner had 10 banks of 100 channels each.
This worked ok for conventional scanners with limited channels. It was easy to partition the systems you wanted to listen to into 10 groups for monitoring. However, when trunking systems came along, things got messy. In addition to having more memory, these scanners had two kinds of
channels: frequency channels for the conventional and trunked system frequencies, and Talk Group ID channels for trunking system talk groups. Some trunking systems required only 4 or 5 control channels to be entered, which wasted the other 95 or so
frequency channels in the bank, but could have hundreds of talk groups...meaning that a single system would have to be entered in multiple banks if you wanted to monitor and track all the ID's.
Trunking radio systems themselves are hard enough to understand, but even if you got that, you now had to learn how to interpret and morph that understanding in order to store the information in your scanner...which did not share a structural organization anything like the trunking systems.
In the real world, radio systems are organized by:
System
Agency
Users
That is, each municipality has some definition of their radio system that includes Agencies (groups of users), then each agency has individual user channels. In a conventional system example (note that all frequencies are made up for this example...):
System: Dallas Public Safety (QK1)
Agency: Police (FQK1)
East Patrol 462.975
West Patrol 462.1375
North Patrol 462.375
CIC 462.125
Agency: Fire (FQK2)
Fire Dispatch 460.875
Fireground 1 460.925
Fireground 2 460.125
Agency: EMS (FQK2)
EMS Dispatch 463.975
EMS Channel 1 463.125
EMS Channel 2 463.375
In a conventional scanner, you would store each user in a channel. If you wanted Bank 1 to be only the police, then you would enter these four frequencies in channels in Bank 1, leaving the remaining 96 channels unused. Similarly for Banks 2 and 3. Or, you could put all of Dallas in Bank 1, then a different city in Bank 2, and so on. The drawback was that it was difficult to turn off single agencies within the city...but it more efficiently used the channels in each bank.
Here's a similar example of a trunked system (again, frequencies and talk group ID's are made up):
System: Fort Worth TRS (QK2)
Frequencies: 862.1275
862.375
863.1275
863.375
Agency: Police (FQK1)
East Patrol 2336
West Patrol 2354
CIC 2406
Agency: Fire (FQK2)
Fire Dispatch 12000
Fireground 1 12016
Fireground 2 12032
Agency: EMS (FQK2)
EMS Dispatch 13004
EMS Channel 1 13020
EMS Channel 2 13036
and so on. (Ignore the QK and FQK for now, we'll get to that, later.) Structurally, the systems look quite similar. However, with a trunked system, the frequency channels are simply an attribute of the system as a whole. Channels look just as they do on a conventional system, but use Talk Group ID's (TGID) instead of frequencies as specific user group identifiers.
In a conventional scanner, this would consume an entire bank...1/10 of the channel capacity of the radio to track even a small system using a few channels.
The BC246T models its memory structure after the real world. Instead of segregating channels into banks, all memory is managed as a pool, from which the user can define distinct systems.
All systems, both conventional and trunked, are organized similarly:
System (with quick key -- QK)
Channel Group (with func+quick key -- FQK)
Channel
Channel
Another Group
Channel
Channel
The user names the system and assigns attributes to the system.
For a conventional system, the main attribute is the quick key assigned to the system (QK). This key functions similar to the bank buttons on a conventional scanner, allowing the user to quickly select/deselect systems by pressing a keypad number while scanning. Unlike a conventional scanner, though, multiple systems can be assigned to the same quick key.
For a trunked system, the major attributes are the quick key and the frequency channels.
Beyond this, trunked and conventional systems are programmed nearly identically. Channel groups are created (these could be for agencies, geographic areas, or however the user wants to organize them). Each channel group can also be assigned secondary quick keys (FQK) that allow quick activation/deactivation of the channel group within the system. Then, channels are programmed into each channel group. For conventional systems, a channel is a frequency and its associated atributes (alpha tag, delay, step, etc). For trunked systems, a channel is a TGID and its assocated attributes (alpha tag, delay, priority, etc).
Each channel takes one memory space. For the above examples, the Dallas system would take up about 14 memory slots (including system and group
overhead) or 24 slots if all channels are alpha tagged and the Fort Worth TRS would take up about 19 memory slots or 28 if all channels are alpha tagged. The remaining memory slots are still free for additional systems and channels. Actual memory usage depends on the features being used, but the above numbers give you an idea of how things are stored.
When scanning, pressing the "1" button would turn on/off Dallas scanning. Pressing F would hold on the current system (let's assume that it is Dallas). Then, continuing to press F while pressing 1 would turn on/off the police channels within the Dallas system. Pressing F+2 would turn on/off both the Fire and EMS channels in the Dallas system, since both groups are assigned to the same F+ quick key.
This method provides complete channel flexibility, while maintaining the functionality of the 0-9 "bank" keys. It also makes turning subgroups on and off much easier...you don't have to be stopped on a channel to change the channel group status; just press F, scroll to the system if it isn't already the active one, then press the number buttons to select the groups to monitor.
My thanks to a friend out there in radioland for this explanation. I am looking forward to seeing this new model and putting it through its paces.
73 all and good hunting,
Larry Van Horn -- N5FPW
Monitoring Times Assistant Editor/Milcom Columnist
Grove Enterprises Technical Support Department
Telephone: V-828-837-9200/F-828-837-2216/800-438-8155
