[TrunkCom] How does New Uniden "Dynamically Allocated Channels" work?

[Larry Van Horn]

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