One Frequency Trunk

[riverradio68]

This is complicated so bare with me. I scan on Uniden scanners. I scan the heck out of DPS and local stuff. I program most all P25 frequencies as a single frequency trunked system then run the scanner in ID search mode. On the P2 scanners this allows me to see specific TG's in use along with user ID's. It's great for getting around the Big E word as many agencies seem to use E on one talk group but not another such as Commerce PD for example. Commerce PD uses TG 3 and 11 the most. 3 seems to be car to car and 11 seems to be the Dispatch channel. 3 is in the clear and 11 is not. This works pretty well on Greenville PD also.

With Texas DPS Let's say Texarkana, I get two major Talk Groups. 1 and 65535. 1 appears to be full duplex and 65535 Only the Dispatcher. User ID 5 shows up on TG 1 and appears to be the console operator. When I get the TG 65535 I then see the 6 digit ID's of the mobile unit. User ID's flow in I see 5 and 6 digit ID's as you would on Richardson or PAWM.

I stumbled across this as Fannin SO is about to move to this format. 4 TG's 3 encrypted leaving Dispatch in the clear but with the ability to secure it when needed. I liked it so much I did this will all P25 conventional and was amazed at how much was actually programed utilizing multiple talk groups on a single frequency.

So my question is, Can this data be submitted to the database? Or does anyone care as long as they can somewhat hear the channel. Oh, this method does not appear to work on Whistler scanners. Only Uniden, so far.

Thanks!

 

[Project25_MASTR]

Just wait until you run into single channel P25 trunking in reality...that's fun stuff right there. To be somewhat more relative though...I've tested the method on Whistler TRX series scanners and it is the only way to get the radio to display conventional TG info. I can only think of a handful of departments using TGID's to segregate traffic on repeaters in the state though because the default conventional TG acts as an all call and overrides everything. Brownfield PD attempted to use it but South Plains Communications programmed radios incorrectly. Gatesville has an OP/mutual use repeater that is shared among PD and Fire using TG's to separate traffic (they are fully encrypted though but that repeater can be utilized as far out as Round Rock). DPS uses is it to be weird...really to maintain resources and better define traffic for logging purposes.

 

[Russell]

I've heard DPS Highway Patrol on TG 1 and what sounded Law Enforcement (Rangers?) on TG 2 on DPS channels many times. Unfortunately, the DB doesn't support One Freq Trunking. Sites and downloads are problematic. We can raise the issue again to see what we get back.

Russell

 

[riverradio68]

Whew, So I'm not alone in this, Awesome! I have told other about this method and they just stare blankly at me. In actuality all digital radios have the capability to do this whether the talk group is strapped or not. I was told by a Motorola guy that users who do not utilize this will always show a default TGID of 1, If you go into XTS software for example, this would be correct and I'm sure APX is no different. I sure could see issues on this with one group being digital and another analog, it looks like it would play havoc with the scanner. I was also told that the site of the repeater has to have a site controller for this to work. A lot of plain jane P25 repeaters have no site controllers at all, So I was told.

Russell, When I see TG-2 or 3 even, though 3 is very rare I am wondering if it's another agency entirely? So TG-2 TPWD and TG-3 UPRR Police? I don't know. But when I saw the 65535 for the first time then recently the 60035 in NCTOG I was like this can't be accidental. But here is the kicker, Fannin for sure is going to this within the next few months, Sherman and Grayson are rumored to be considering it, Commerce already has done it so it's not as scarce as it was in the early days of P25.

Instead of submitting the data to the database as WXX445 | 155.0000/153.0000 NAC 4CE Partial encrypted TAG

Submit it as we already do with a DMR II system which operates much the same way as P25 One Freq Trunking. It might be confusing at first to some but it also might push the scanner users to program this way and open, no Blow the door off the hinges and see what's actually in their local radio network rather than the single channel and NAC.

P25-MASTR, I tried to program this on a TRX-1 and a WS1080 and had no luck and I think it was because there was no way to input the NAC code. How did you manage to do it?

Thanks for the feedback Guys!

 

[KI5IRE]

So let me get this right, the DPS frequencies I’ve been scanning as conventional P25 frequencies are actually trunked?

If I program every P25 frequency as a single frequency trunked will it still scan?

How exactly do I program this correctly? Say for instance, the common statewide channels or the DPS Region 1 channels? Would I have to make a completely new system for each frequency I program as a site? Would each frequency i.e. the dispatch and mobiles to dispatch frequencies be completely different systems or just different sites?


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[nd5y]

So let me get this right, the DPS frequencies I’ve been scanning as conventional P25 frequencies are actually trunked?

No.

 

[rattlerbb01]

So let me get this right, the DPS frequencies I’ve been scanning as conventional P25 frequencies are actually trunked?

If I program every P25 frequency as a single frequency trunked will it still scan?

How exactly do I program this correctly? Say for instance, the common statewide channels or the DPS Region 1 channels? Would I have to make a completely new system for each frequency I program as a site? Would each frequency i.e. the dispatch and mobiles to dispatch frequencies be completely different systems or just different sites?


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The repeater cannot carry two conversations at a time, hence it is still conventional P25.

I have poked around a little with the P25 repeaters in OFT mode on my 436, and I have not caught a talkgroup that is not 1 yet myself. I'll check some more of the stuff in my area to see what comes up.

OFT can create quite a robust "system" in some areas using conventional networked DMR. When I was in Oklahoma last year, Okmulgee County was difficult to figure out at first until I just set up each of the 5 "areas" that towers were in (N, E, S, W and Central) with the frequencies for the respective repeaters, then set up talkgroup departments for each town and county agency. It is still conventional, but scans like a trunk system flawlessly.

 

[IAmSixNine]

DPS uses conventional P25.
As mentioned by another user P25 Conventional still uses a TG. The default is 1, but it can be between 1 and 65534. I believe 65535 is more of an all but scanners and radios are different with that. But not really relevant. I have never seen anything other then TG 1 for the DPS Garland main channel. But maybe ill have to make some changes to how i monitor it to see if other TGs are used.

 

[motorola_otaku]

I program most all P25 frequencies as a single frequency trunked system then run the scanner in ID search mode. On the P2 scanners this allows me to see specific TG's in use along with user ID's. It's great for getting around the Big E word as many agencies seem to use E on one talk group but not another such as Commerce PD for example. Commerce PD uses TG 3 and 11 the most. 3 seems to be car to car and 11 seems to be the Dispatch channel. 3 is in the clear and 11 is not. This works pretty well on Greenville PD also.

This is actually called P25 Conventional Talkgroup and isn't technically trunking as there is no central controller involved. Each individual radio is programmed with a talkgroup list, and individual talkgroup IDs can be strapped to a channel or made selectable from the menu (assuming the radio has a display and keypad, if it's a portable.) Radios can also be programmed to listen for both a matching talkgroup and NAC to unmute (receive) or to unmute on any traffic with a matching NAC. It's widely used on ham P25 systems and as you've noticed encryption keys can also be strapped to talkgroups.

Also, the reason you see RID 5 on DPS dispatch everywhere is because that's the default radio ID in a DIU3000.

 

[Project25_MASTR]

To add to what otaku stated, the repeater doesn't care. If the NAC matches either it's receive NAC, the multi-NAC list, or is a valid NAC (in the case of F7F repeaters)...it will pass the traffic regardless of if encryption or talkgroups are being used. Keep in mind, there is true single channel trunking as well (Icom has a P25 repeater that will function as such and is a capability with both Kenwood (EFJ) Atlas and Etherstack P25 systems).

The one problem with the TG method (versus multi-NAC) when it comes to separating traffic on a conventional system...if someone forgets to enable the TG on a channel and leaves the default talk group in place...the unit running as the default talk group can hear all traffic on the channel (regardless of TGID) and will be heard by all units on the system regardless of selected talkgroup.

 

[riverradio68]

This makes sense, I know our county is moving to this and they have to have site controllers installed. There was a big fuss over whether to encrypt the TG or the frequency. Last check the citizens won and they are going to E the TG only.

Interesting stuff gentlemen! I guess to save scanner space I could go back to conventional on DPS as it seems I won't be loosing anything. Commerce PD on the other hand seems to be using "the controller" as they have 3 TG's in use. (or that's what I am logging). Thanks for the education!

 

[Project25_MASTR]

This makes sense, I know our county is moving to this and they have to have site controllers installed. There was a big fuss over whether to encrypt the TG or the frequency. Last check the citizens won and they are going to E the TG only.

Interesting stuff gentlemen! I guess to save scanner space I could go back to conventional on DPS as it seems I won't be loosing anything. Commerce PD on the other hand seems to be using "the controller" as they have 3 TG's in use. (or that's what I am logging). Thanks for the education!

Just because you have talk groups in place doesn't mean you are using a controller. In most common P25 setups, a controller (of some sort) is only needed when traffic need to be segmented and passed to multiple sites. Any P25 repeater (it's part of the spec) can repeat TG info and keep the TG's separate. Actually even in trunking, the voice channel doesn't know anything regarding the TGID. Only the subscriber radios care in a conventional system.

 

[riverradio68]

Just because you have talk groups in place doesn't mean you are using a controller. In most common P25 setups, a controller (of some sort) is only needed when traffic need to be segmented and passed to multiple sites. Any P25 repeater (it's part of the spec) can repeat TG info and keep the TG's separate. Actually even in trunking, the voice channel doesn't know anything regarding the TGID. Only the subscriber radios care in a conventional system.

I hear what your saying and I get it. Fannin County in it's infinite wisdom is buying into this single frequency multiple talk group thing which is why I started to experiment with it in the first place. Personally with everything I have heard I think they are going to be very disappointed with the outcome. But it's not my money or any other tax payers money. They are doing this with a private donation. Site controllers are to be a part of it so that they can simulate? trunking? does that sound about right?

Anyways, the feed back you all have offered has been great. I rebuilt my DPS scan lists last night dropping the single frequency trunk (As Pro Scan calls it). and reverted back to P25 conventional. I DO however see this option as a really good option when programming Tier II DMR. Say the McKinney 145.3500, Set as Single Frequency DMR then adding Brandmeister and the static TG's and scanning, This method hears the site better than the radio well at least better than the MD-9600.

Again, thanks for the feed back, good stuff!