MPT-1327 question, hope it don`t sound like a dumb one .

[N9NRA]

Hey there, i`ve read about these MPT-1327 trunking systems, and know that apperently they`re not trackable by currently availible scanners. What`s been nagging me to know is, what is it about these syetems that is the reason for not being able to be tracked by currently availible units? Just curious. Thanx! N9NRA

 

[Jay911]

Mainly a lack of popularity. There are very few MPT1327 systems in the areas where scanners sell big, so to a manufacturer, it makes little sense to spend time putting the protocol in their scanner.

It's a free, open source protocol, though, so you never know if it might appear as a value-added firmware upgrade one of these days.

 

[N9NRA]

Ya know, i kinda wish they would add it, even if i had to pay to get that capability i`d give it a passing wink, the other reason i asked was that from what i`ve read the systems seem to be set up with seprate data/control channels for each group of voice freqs. A while back Wood County (WI) was looking to switch to one of these systems, but the attempt appears to have collapsed for the time being for some unknown reason. Thanx for the answers guys, the knoledge is appreicated. N9NRA

 

[Comint]

. . . . from what i`ve read the systems seem to be set up with seprate data/control channels for each group of voice freqs.

Don't quite understand that comment. MPT1327 uses Control Channels and Traffic Channels, with the latter being used for both Voice and/or Data. A Site can have up to 24 Channels.

Under MPT1343, Users of very busy Sites can be divided into four separate Control Categories (A, B, C, or D) to spread the load across the Channels. Ideally, this needs to be set up from the beginning, as every radio has to be programmed for this feature.

The last digit of the SysID signifies if Control Categories may be in use.

SysID ends in 1 or 9 - All Categories permitted
SysID ends in 2 or A - Categories A & B only permitted
SysID ends in 3 or B - Categories C & D only permitted
SysID ends in 4 or C - Category A only permitted
SysID ends in 5 or D - Category B only permitted
SysID ends in 6 or E - Category C only permitted
SysID ends in 7 or F - Category D only permitted

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Comint

 

[N9NRA]

That`s kinda what i was getting at, and ya explained it to me very well, thanks for the info, when i read of the one here in WI that was supposed to be comming online in Wood County (now offline for some reason, don`t know if/when it will come back) i got to wondering why they couldn`t be tracked. I thought it was because of the system sending data on both control and voice channels, and current scanners can`t handle that kind of system. Oh well, mabey in the feuture we`ll get that feature as an add-on. Thanks for the answers! N9NRA

 

[Comint]

Possibly slightly off topic.

Of the seven main Trunked Radio protocols around the world (Motorola, EDACS, LTR, MPT1327, SmartTrunkII, TETRA, and TetraPol), only three are currently supported by scanner manufacturers, and while there is some hope for MPT1327 support, I don't expect to see the last three supported 'anytime soon'.

As for sending Data and Voice over the Traffic Channel: I don't see any big problem with that for a scanner, as the Trunking System Controller (TSC) indicates whether the transmission is Voice or Data in the GTC (Goto Traffic Channel) message. Programs such as TrunkView, and I think UniTrunker*, handle it without any problems, only changing to the Traffic Channel for Voice messages, and ignoring the Data messages, as most scanner users are only interested in the Voice messages. Besides, a lot of Data messages are in proprietary formats, and cannot be decoded.

* haven't used UniTrunker on an MPT1327 system for quite some time, so my memory is a bit rusty.

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Comint

 

[Jay911]

Trunkview definitely logs the data info. The MPT system in St. John's, Newfoundland, sends a ridiculous amount of data constantly - looks like every time a bus hits a bus stop, it sends a trigger down the trunk system.

I would suspect that UT logs it in the background too, but I haven't been in NL for nearly a year.

 

[Comint]

Jay911

There are two types of Data which can be sent on MPT1327/1343 systems.

1. Short Data Messages (SDM) - max 184 bits - which are sent over the Control Channel, and

2. Lengthy Data messages which are sent over a Traffic Channel, and which TrunkView ignores, as in NOT changing to the Traffic Channel and unmuting the Squelch. Of course, the relevant GTC Data message still shows in the logfile, but the listener does not hear the Data stream.

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Comint

 

[Jay911]

Indeed - my point being, short data messages are definitely supported by at least one of the two programs you mentioned.

 

[grant]

MPT1343 messages

The local MPT1327/43 system runs close to 20 channels.

This is a selection of the short messages .... looks they there limited locally to 25 characters

UR PUMPING
WAIT FOR ORDER
BLACKWATTLE B RET 3017
PRESTONS CONC RET 3053
SILVERWATER LOAD 3057
910AM PADNGTN 2 CT P10
OUT OF SQ SND:8LVI-SI
INT VBUSY NO CABS
TA
TRY 75
ACCEPT CHECK IN 08:42
9AM F!FOREST CT $65
MAKES V UGLY
SAW U GO PAST
WHAT U EXPECT
2 BALMAIN
GRANNY
RTRN DETAILS PL

and so on

Grant

 

[Comint]

The local MPT1327/43 system runs close to 20 channels.

This is a selection of the short messages .... looks they there limited locally to 25 characters

UR PUMPING
WAIT FOR ORDER
BLACKWATTLE B RET 3017
PRESTONS CONC RET 3053
SILVERWATER LOAD 3057
910AM PADNGTN 2 CT P10

----- snip -----

Grant

Well, at 8 bits per character, the 184 bits maximum would allow for a max of 23 characters. At 10 or 11 bits, it would be even less.

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Comint