Question on GATRRS / Motorola Talk Group Patching - Travis vs. Wilco (or any inter-county system)

[KTR722]

Question for anyone that is a radio tech or knowledgeable on this subject. I have noticed from watching both SDRTrunk and Pro96Com over the past few months that there seems to be several ways that the system allows you to establish a "patch" between two talk groups.

Can anyone shed some light on how patches are made in a Motorola P25 system and if there are multiple methods for doing this? Presumably there are limitations with each method? Is one method preferable over the other....

For example, GATRRS Travis County has Austin Fire FCOM N & FCOM S in a constant patch (same goes with FCOM E/W). This patch is visible on Pro96Com on the patches tab of that application. I will see ABI EM1 and ABI COM often patched together also - Same with Pflugerville PD patching their A and B channels together. If the Travis County Jail needs to broadcast a message to all of its talkgroups, I will see a patch initiated in Pro96Com that patches probably 6-8 talkgroups together for a few seconds while they transmit the broadcast. When Talkgroups patched together like this get transmitted on, it looks like from SDR and Pro96Com that only one actual frequency gets used and any radio that happens to be listening to any TG that the patch is applied to will tune in to that one specific freq.

OTOH, I almost never see Wilco doing a patch in this manner. Instead, when they patch two channels together, it does not show up as a patch on Pro96Com. From watching the display on Pro96Com, I see two frequencies being used, one for each talk group that has been "patched" together (which seems inefficient from a resource standpoint). From an architectural standpoint, this looks to me more like a simulcast and not a patch but that is not how they refer to it over the air.

Not to complicate the above, I also see some interesting stuff on Hays county and Bell county on how they will patch 2 talk groups into a third "temporary" Talk group (usually starts with 64xxx or 65xxx) for paging purposes. I presume this is to patch their P25 systems into either OpenSky (Hays County) or EDACS (Bell County). These patches are mostly annoying in that, if you want to listen in on the pages on the Broadcastify Calls platform, it only recognizes the 64xxx or 65xxx talk group (and not the talk groups being patched), and this temporary TG list is 100 talk groups that get selected in sequence, which is too many to plug into a Broadcastify Calls playlist (which is limited to 20). The other TGs getting patched are not recognized by the Calls platform so you end up never hearing the page/dispatch going out.

Anyone knowledgeable on this please chime in. Given our current fire weather forecast, patching across systems over the next few weeks is probably going to become a daily occurrence.

 

[KevinC]

Question for anyone that is a radio tech or knowledgeable on this subject. I have noticed from watching both SDRTrunk and Pro96Com over the past few months that there seems to be several ways that the system allows you to establish a "patch" between two talk groups.

Can anyone shed some light on how patches are made in a Motorola P25 system and if there are multiple methods for doing this? Presumably there are limitations with each method? Is one method preferable over the other....

For example, GATRRS Travis County has Austin Fire FCOM N & FCOM S in a constant patch (same goes with FCOM E/W). This patch is visible on Pro96Com on the patches tab of that application. I will see ABI EM1 and ABI COM often patched together also - Same with Pflugerville PD patching their A and B channels together. If the Travis County Jail needs to broadcast a message to all of its talkgroups, I will see a patch initiated in Pro96Com that patches probably 6-8 talkgroups together for a few seconds while they transmit the broadcast. When Talkgroups patched together like this get transmitted on, it looks like from SDR and Pro96Com that only one actual frequency gets used and any radio that happens to be listening to any TG that the patch is applied to will tune in to that one specific freq.

OTOH, I almost never see Wilco doing a patch in this manner. Instead, when they patch two channels together, it does not show up as a patch on Pro96Com. From watching the display on Pro96Com, I see two frequencies being used, one for each talk group that has been "patched" together (which seems inefficient from a resource standpoint). From an architectural standpoint, this looks to me more like a simulcast and not a patch but that is not how they refer to it over the air.

Not to complicate the above, I also see some interesting stuff on Hays county and Bell county on how they will patch 2 talk groups into a third "temporary" Talk group (usually starts with 64xxx or 65xxx) for paging purposes. I presume this is to patch their P25 systems into either OpenSky (Hays County) or EDACS (Bell County). These patches are mostly annoying in that, if you want to listen in on the pages on the Broadcastify Calls platform, it only recognizes the 64xxx or 65xxx talk group (and not the talk groups being patched), and this temporary TG list is 100 talk groups that get selected in sequence, which is too many to plug into a Broadcastify Calls playlist (which is limited to 20). The other TGs getting patched are not recognized by the Calls platform so you end up never hearing the page/dispatch going out.

Anyone knowledgeable on this please chime in. Given our current fire weather forecast, patching across systems over the next few weeks is probably going to become a daily occurrence.

WilCo is probably using Multi-select (MSEL), which will key up all the resources individually. Not very efficient as you said. Probably a training thing.

 

[KTR722]

WilCo is probably using Multi-select (MSEL), which will key up all the resources individually. Not very efficient as you said. Probably a training thing.

Good stuff, thanks Kevin...now I have a name to what I am observing. Do you know how Travis County is doing their patches (or have a name for it)?

I had noticed for a while that Wilco patches were not showing up on Pro96Com. I had observed other bizarre behavior on that app (example: all 15xxxx radio IDs on Hays county almost always come across with a UID of "0", while all the 83xxxxx come across perfectly). My theory on that now is that the 15xxxx radios are OpenSky radios being patched into the P25 system, and Pro96Com is somehow not setup to capture those UIDs, although they come across clean on my SDS).

What caught my attention was watching WCSO one night working with DPS, and they had CALL 2 "patched" into one of the A1 R LE interop channels. Watching the display on SDR, I was seeing the same radio UID keying up on three separate frequencies. One was on CALL 2 (ENC of course), and the other 2 were both on the A1 R LE talkgroup, but 2 different freqs. Presumably this was because one freq was on a Wilco tower and the other was one a TC tower.

 

[KevinC]

Good stuff, thanks Kevin...now I have a name to what I am observing. Do you know how Travis County is doing their patches (or have a name for it)?

I had noticed for a while that Wilco patches were not showing up on Pro96Com. I had observed other bizarre behavior on that app (example: all 15xxxx radio IDs on Hays county almost always come across with a UID of "0", while all the 83xxxxx come across perfectly). My theory on that now is that the 15xxxx radios are OpenSky radios being patched into the P25 system, and Pro96Com is somehow not setup to capture those UIDs, although they come across clean on my SDS).

What caught my attention was watching WCSO one night working with DPS, and they had CALL 2 "patched" into one of the A1 R LE interop channels. Watching the display on SDR, I was seeing the same radio UID keying up on three separate frequencies. One was on CALL 2 (ENC of course), and the other 2 were both on the A1 R LE talkgroup, but 2 different freqs. Presumably this was because one freq was on a Wilco tower and the other was one a TC tower.

With MSEL you will only hear the dispatcher on multiple resources, the mobiles will only be heard on whatever TG they are on.

RID of "0" usually means a patch from a conventional resource or some other non-P25 source.

And I "believe" the DPS air resources can patch stuff from their aircraft, so another wrench to add to the confusion.

 

[KTR722]

With MSEL you will only hear the dispatcher on multiple resources, the mobiles will only be heard on whatever TG they are on.

Listening to the radio traffic on several of these Wilco patches, there are mobile radios on different TGs that are able to talk to each other directly, so if MSEL is basically the dispatcher keying up on multiple talkgroups simultaneously, then there is some other kind of patch going on. I have seen the same type of patch in place for the FD/EMS side to allow mobiles to talk to each other and it will not show up as a patch. Cedar Park a few months ago patched their FD and PD channels together while searching for a missing child, same type of situation.

 

[Russell]

...
And I "believe" the DPS air resources can patch stuff from their aircraft, so another wrench to add to the confusion.

DPS can, indeed, patch from the helicopters. They'll commonly patch resources in the DFW area.

 

[KI5IRE]

Not to complicate the above, I also see some interesting stuff on Hays county and Bell county on how they will patch 2 talk groups into a third "temporary" Talk group (usually starts with 64xxx or 65xxx) for paging purposes. I presume this is to patch their P25 systems into either OpenSky (Hays County) or EDACS (Bell County). These patches are mostly annoying in that, if you want to listen in on the pages on the Broadcastify Calls platform, it only recognizes the 64xxx or 65xxx talk group (and not the talk groups being patched), and this temporary TG list is 100 talk groups that get selected in sequence, which is too many to plug into a Broadcastify Calls playlist (which is limited to 20). The other TGs getting patched are not recognized by the Calls platform so you end up never hearing the page/dispatch going out.

This is how patching is done on most Harris systems the I’ve scanned. Both the Hays (LCRA) and Bell County systems are Harris systems. Most Harris systems Broadcast to all the the talkgroups selected, plus the temporary group that is created (64xxx/65xxx) during the patch.

As far as GATRRS, it’s a Motorola system and the way that you’re setting patching on the FCOM channels is generally how I’ve always seen patching done on Motorola systems. No temporary talkgroups are created like Harris systems.