P25 Patch Following

[Jay911]

Hi all,

The provincewide Alberta P25 (Phase 1) network that Harris is currently building out is getting more and more functions tested as time goes by, and one of them has been discussed here in the past. I'm a little confused by the concern people have raised vs what I've witnessed and I want to get an idea of what I should be looking for.

I have seen people here mentioning that P25 patch following is not supported in current or past Uniden models (let's say the x36 and HP1/HP2 lines - I have a 436, 536, and two HP1s in use). Here's why I'm confused about that.

The P25 system I'm monitoring (see link above) has several test talkgroups, in the 148xx-149xx range. The other day, while fiddling with Unitrunker, I saw that a nearby site had four of those TGs patched together; the patch ID, according to UT, was 2001.

I heard all the comms I expected to hear all day long, including on the talkgroups that were members of that patch group.

Am I missing something? If the radios aren't following patches properly, shouldn't I have either not heard anything, or, since my radios are set to ID SEARCH mode, heard comms on "talkgroup" 2001 instead of 14851/2 & 14953/4?

 

[Jeff19]

I am located in a jurisdiction where a phase II P25 system routinely patches groups of two TG's together. My experience has been that only one of the TG's on my 436 hits for activity on either TG. There also seams to be no rhyme or reason as to which TG appears active. E.G. TG's A2 and A16 are always patched - sometimes I hear all the activity on A2, other days (or hours) I hear activity on A16.

The problem for me is that without monitoring both TG's, I cannot "hold" on one without already knowing which TG is hitting on the scanner at the time.

 

[troymail]

I am located in a jurisdiction where a phase II P25 system routinely patches groups of two TG's together. My experience has been that only one of the TG's on my 436 hits for activity on either TG. There also seams to be no rhyme or reason as to which TG appears active. E.G. TG's A2 and A16 are always patched - sometimes I hear all the activity on A2, other days (or hours) I hear activity on A16.

The problem for me is that without monitoring both TG's, I cannot "hold" on one without already knowing which TG is hitting on the scanner at the time.

I'm assuming this is PG County... Are A2 and A16 really "patched" in the normal sense of "patching" (i.e. can you see the patch setup on Pro96Com?). There are a number of methods for doing patching - some that are exposed in the system data and others that are not. True patches are really temporary but the PG setup (which is becoming more and more common) are a permanent configuration.

I'm out of the area right now but when I return I'll take a look (unless you beat me to it).

 

[Jeff19]

Yes...PG. I didn't realize there are different methods to "patch" two TG's together.

Another thing I have noticed regarding PG TG 2/16...generally when the transmissions "appear" on TG 2, they are in Phase I, and on 16 they are in Phase II. I understand why the talkgroup drops back to Phase I (when a non Ph II radio affiliates,) but the active talkgroup (as it appears to the 436) appears to be associated with the Phase the TG is transmitting in.

 

[Steve2003]

I would love to see the support for P25 patching on the BCDx36HP models. I have noticed two different types of patching:


On Harris systems a SAID (system assigned ID) is used whenever talkgroups are patched. These change each time a patch gets added, but if you log with Pro96Com for a few days you should be able to determine the range of SAID TGs (the system I monitor uses 100-199). The only solution on the BCDx36HP scanners is to leave the system you are monitoring in ID search mode or create a department with all the SAID TGs.

On Motorola (and I presume other systems), one or more talkgroups can get patched to another Talkgroup already in use. When this happens there is no way to monitor unless you monitor the target/destination TG.

Uniden has patching figured out on EDACS, but this has been a thorn in my side ever since I started using Uniden scanners to listen to P25. UpMan stated that there are several phases of updates planned for the BCDx36HP line of scanners, hoping P25 patching will be one of them.

 

[Jay911]

That's excellent info, Steve, thanks very much! Hopefully UPMan sees that. I'll have to keep an eye on this system and see if I was hallucinating the other day.

 

[tbiggums]

The P25 system I'm monitoring (see link above) has several test talkgroups, in the 148xx-149xx range. The other day, while fiddling with Unitrunker, I saw that a nearby site had four of those TGs patched together; the patch ID, according to UT, was 2001.

I'm pretty sure Unitruker doesn't support decoding the patch messages on the control channel for Harris systems yet. At least not on version 1.0.29.5. It does decode the Motorola P25 patch messages, though. Pro96Com works with both. Problem is, neither the Motorola or Harris patch messages are part of the P25 standard.

I have heard that newer Harris systems might be able to support using the Motorola patch control channel message. Next time you see a patch set up on that system, set Unitrunker or Pro96Com to write to a log file, and see if you can see if the patch message has the Manufacturer ID of 0x90. If so, they're probably using the Motorola patch message format (probably to allow compatibility with older Motorola P25 radios).

I won't be buying another Uniden scanner until they support P25 patches on both Motorola and Harris systems.

Harris systems using their proprietary SAID patch message are the worst to listen to without proper patch following. You have to keep the entire SAID range open, and listen to any patches that might be made, even if they're not for the talkgroups you're interested in. You can temporarily lock out these patches after you listen to them and verify the people talking are not from the talkgroups you're interested in, but it's quite the hassle to deal with.

 

[Jay911]

Couple of things -

1. Your UT is out of date. I'm using preview 31.6 (and I'm two sub-versions behind, myself); 30.10 is the latest non-preview release.

2. I always log. The system is not using Motorola patches - it's using Harris patches.

From 4/12 when I noticed the patching:

 -B0 A4 61 07 D1 00 00 80 3A 6A 1C 22 Super DEAC adds G 07D1 status 3A6A
 -BA 00 61 30 5B 61 61 00 BA 70 11 FB RFSS Status Broadcast Mfg 00 LRA 61 Sys 05B Sub 61 Site 61 Activechannel 0-0BA(771.40625) (data,voice,registration)
 -B0 A4 61 07 D1 00 00 80 3A 03 E1 AD Super DEAC adds G 07D1 status 3A03
 -BB 00 61 66 0C 50 5B 00 BA 70 6F 24 Network Status Broadcast Mfg 00 LRA 61 WACN 660C5 Sys 05B channel 0-0BA(852.16875)(data,voice,registration)
 -B0 A4 61 07 D1 00 00 80 3A 04 91 4A Super DEAC adds G 07D1 status 3A04
 -B3 00 83 A5 80 64 09 2B 0C BA 0C 85 Identifier Update 8 Base 769081250 Spacing 12500 Tx Offset 30000000 Slots 2
 -B8 00 FF 0F 6C 00 0F 6C 00 01 9C 83 System Service Broadcast Available 0F6C00 Supported 0F6C00
 -B0 A4 61 07 D1 00 00 80 3A 69 2C 41 Super DEAC adds G 07D1 status 3A69

There are, unfortunately, no channel grants in my logs, but the next time I see them on a patched channel, I will certainly be examining the data.

 

[troymail]

Yes...PG. I didn't realize there are different methods to "patch" two TG's together.

Another thing I have noticed regarding PG TG 2/16...generally when the transmissions "appear" on TG 2, they are in Phase I, and on 16 they are in Phase II. I understand why the talkgroup drops back to Phase I (when a non Ph II radio affiliates,) but the active talkgroup (as it appears to the 436) appears to be associated with the Phase the TG is transmitting in.

Back in the area and looking at the Prince George system on Pro96Com...

I see some patches popping in and out:
181->25
19->13
1->7
49->55
31->25

Believe these are all police talkgroups.

However, I am not seeing 8A2 or 8A16 patched at all.

For a time, I was seeing both 8A2 (1135) and 8A16 (1137) active simultaneously - with 8A2 in Phase 1 mode while 8A16 was Phase 2 mode. Right now, I generally only see 8A2 active in Phase 1 mode so the 8A16 user must have left the talkgroup or system.