mcems79
Member
why are there so few tower sites in the state for this system? there are a whole lot of alabama counties left uncovered and i was wondering if anyone know are they still building this system out ?
AIRS sites
- Thread starter mcems79
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Unlike most "statewide" systems, AIRS is more of a "system of systems". The system started out using Huntsville/Madison County's Motorola P25 core if I'm not mistaken. Then at various points, Birmingham/Jefferson County, Baldwin County, Tuscaloosa County and Dothan built out additional cores. These counties were also responsible for building out their own tower sites. After these cores were in place, some counties near each of them contracted with the owner of the core to join their system, leaving them only responsible for the cost of additional tower sites and radios (and subscriber fees).
The core is the "brains" of the system that controls management and operation of the trunking system. You can have multiple cores broken down into different Radio Frequency Sub-systems, like is the case with AIRS. You can tell which core that sites belong to by looking at the RFSS ID.
To my knowledge, the State of Alabama has not built out any cores or tower sites. Instead, they left it up to the individual counties to make it happen. As such, the majority of the system users are large cities and counties that would likely have their own P25 system regardless of whether AIRS existed or not. Even without the cost of a core, smaller rural counties usually do not have the funds to build out their own P25 sites, buy radios, and pay subscriber fees.
The core is the "brains" of the system that controls management and operation of the trunking system. You can have multiple cores broken down into different Radio Frequency Sub-systems, like is the case with AIRS. You can tell which core that sites belong to by looking at the RFSS ID.
To my knowledge, the State of Alabama has not built out any cores or tower sites. Instead, they left it up to the individual counties to make it happen. As such, the majority of the system users are large cities and counties that would likely have their own P25 system regardless of whether AIRS existed or not. Even without the cost of a core, smaller rural counties usually do not have the funds to build out their own P25 sites, buy radios, and pay subscriber fees.
mcems79
Member
oh ok, that makes sense. here in mobile county we used to operate on a harris edacs system and we had those airs sites in mobile were active. when we went to our own harris p25 system those sites were shut off and i know alea troop A uses our system for coms but i'm not sure if say baldwin county units came over here could use our system on their talk groups or not.
There are many ways that Baldwin County AIRS users could have interoperability with Mobile, however it all comes down to whether the appropriate planning and investment took place. Politics and procedure is also a big issue. I have no idea if some of these are in place in that region, but here's some of the ways interoperability could be achieved:
- I'm pretty sure that all of the Alabama Mutual Aid Tac channels on AIRS are connected to both Harris systems in the state via P25 ISSI. This would allow users from any of the systems to communicate with each other on these channels.
- Baldwin County AIRS users could have Mobile County's system programmed into their radios, and vice-verse. The radios are technically capable, but again it would come down to politics, procedure and planning. Law enforcement from both agencies utilize lots of encryption, so either some keys would have to be shared, or the communications could take place in the clear. Specific interop talkgroups could be setup for this.
- Talkgroups from any system, or conventional channels could be patched together from dispatch consoles or interoperability gateways like the JPS ACU. This is not as seamless as the other options, as it is basically just an audio and PTT/COR connection. Radio IDs and emergency signalling do not get passed from one system to the other, and audio quality usually suffers slightly.
It's been speculated that there is some patch ability setup between AIRS and the Mobile system. There have been some 62xxx range temporary talkgroup IDs pop up in the past, all encrypted, that may be part of the patch. But with no radio IDs and no clear audio it's hard to know for sure.
I was also under the impression the AIRS towers in Mobile were still active. Our Medstar units often go over to USA or Infirmary and are still in radio range. I don't know how they could stay in communications otherwise, I doubt Spanish Fort or Fairhope sites reach that well across the bay and across downtown.
I was also under the impression the AIRS towers in Mobile were still active. Our Medstar units often go over to USA or Infirmary and are still in radio range. I don't know how they could stay in communications otherwise, I doubt Spanish Fort or Fairhope sites reach that well across the bay and across downtown.
mcems79
Member
interesting, i will have to check that again. i couldn't find a control channel the first time i scanned it but i could have put something in wrong. i'm still learning how to use my sds200. it's also nice to mee a fellow ems person into scanning. i work for mcems and fire dispatch on the night shift.
mcems79
Member
lol you are correct about the high stress situations. i appreciate all of the knowledge i'm still trying to learn about a lot of this stuff and still learning how to use my sds200.
I was under the impression the 00A, 673AE sites were abandoned years ago. I remember seeing at least one post stating such.
Because this is/was a Harris system, it was really always a separate system from AIRS. It would have required either an ISSI bridge, or gateways/patches for each talkgroup that was shared between systems. Also, subscriber radios would not seamlessly roam between systems. It would require manually swapping between the two.
For anyone close enough to listen, it would be worth monitoring to see if these sites are still broadcasting a control channel.
mcems79
Member
i live in mobile so i'm going to check them out again and see what i can find.
I'm not an EMS person, sadly, just a listener.
How do you like that scanner so far? I keep wondering if I should pick one up despite the high cost. Right now I use an SDR on my PC with SDR Trunk software and it works pretty good, but bit I'm limited to what I can hear from home. I put a discone and a UHF bean up at around 35 feet above ground level but it actually made my reception worse for the AIRS systems, go figure. I'm thinking a dedicated scanner would work better than a general purpose SDR for this purpose.
There are examples of this with South Alabama, where S&P Communications has a VHF NXDN system across multiple counties: Covington, Coffee, Crenshaw, Geneva, Pike; or MetroLink with a VHF NXDN system originally in Houston and Henry Counties, now just Henry. The S&P system covers counties with very rural areas, I'd say the VHF NXDN build was a great way to go.
With that said, now those areas are locked into that ecosystem and it works for them.
Dothan (Houston County) used to independently operate their 800 MHz simulcast P25 system. Dale County was on a Motorola P25 system, while Ozark (in Dale County) was using a Harris P25 system. There was no easy interoperability between the three. If Dale County SO & Ozark PD needed to interop, the dispatcher had to make a patch.
Flash forward, Ozark transitioned to AIRS, and Ozark left Harris and went to Dale County's Motorola P25. Here's the interesting part, Dothan's zone is 6. Dothan and Ozark utilize the 6xxxx TGID convention. Dale County is still utilizing the 2xxxx TGID convention... But Dale County and Ozark are using the same system and frequencies. There were some growing pains for Dothan at first, but the system is pretty solid. Dale County and Ozark seem to intermittently have issues. Perplexing at times.
