NTIRN I/O Talkgroups - which sites?

[willdanl]

Are the I/O talkgroups (I’m specifically interested in the Law I/O ones) always carried on certain sites/layers throughout the system, or are they dynamic, and determined by the locations of the subscribers on any given TG while in use? At one time I thought (probably mistakenly) that they were always on all sites/layers - but a few weeks ago, I could listen to activity in East Tarrant County on a Law I/O channel on Site 4 in Johnson County, but it wasn’t coming through on FW Layer 2 - I was in range, hearing FWFD. I didn’t have Layer 1 programmed in so I couldn’t test that. Thanks for any insight. Trying to figure out how to program some radios to catch the Law I/O TGs anywhere in the NTIRN footprint next time I‘m in the area.

 

[BenScan]

I believe the Call channels come across virtually all sites. The others are likely only going to be heard if there's at least one radio affiliated on a site. However, since there's so many radios spread across the Metroplex, you'll often hear them on many sites.

In Fort Worth, Law IOs will be on Layer 1 and Fire IOs on Layer 2.

 

[Alliance01TX]

Howdy - I can confirm that in the NTIRN - Netcom (NE Tarrant - Site 3) we have the FTW LAW I/O, FIRE I/O, PW IO and HOSPITAL IO in our PD and Fire Radios, along with other "InterOp" channels (DFW Airport, Denton County I/O...etc..)

In fact, a couple days ago we had emergency radio maint on our part of NTIRN System and we had all PD and Fire switch over to LAW I/O-10 and FIRE I/O-10 for a few minutes, as I recall...Ben has the details on the layers nailed I think.... Side note: We had Netcom PD/Fire HT Radio/s with us a few weeks ago at the Fort Worth Fire Training Center in the area of South I-35 @ I-820 and we were picking up Netcom traffic from NE Tarrant perfectly, so the coverage is very good in my opinion and likely we were handed off to another Site I would suspect that far south as well....

 

[Project25_MASTR]

Region wide Interoperabile talkgroups on all P25 systems in Texas are capable of being carried by all sites within the system (some even to other systems). Fort Worth Layer 1 and 2 are oddities as the sites are all physically co-located (i.e. provide the same coverage) but the split to prioritize traffic while increasing capacity of the overall system. Out side of some of the dual layer limitations though, interop groups operate as standard wide area trunking groups (i.e. someone has to be affiliated to the group locally for the system to pass it's traffic).

 

[blantonl]

Fort Worth Layer 1 and 2 are oddities as the sites are all physically co-located (i.e. provide the same coverage) but the split to prioritize traffic while increasing capacity of the overall system. Out side of some of the dual layer limitations though

Fort Worth never forgot what happened with their Type II controller during the Tornado In 2000 😂. You can sense it in all their architectural decisions

 

[Project25_MASTR]

Fort Worth never forgot what happened with their Type II controller during the Tornado In 2000 😂. You can sense it in all their architectural decisions

I mean, you look at a 6809 wrong and it goes into failsoft…

The reality is though up until the switch over to Astro 25 releases greater than 7.15 one of the limitations of simulcast with Motorola was that you could only have 20 channels in a simulcast cell which was due to the limitations of a T1. In order to provide additional capacity, you add another layer to the system. The City of Austin did something very similar with their County Wide/East 620 overlays though East 620 didn't have the exact same footprint as County Wide. Now you'll notice, City of Austin has since built to a full 30 channels and combined the two layers as it provides more capacity compared to two 20 channel layers (just one of the weird facts about trunking, two 20 channel sites have the same call handling capacity as a single 21 channel site as everytime you add a channel, you double your call handling capacity).