Question about Alabama Interoperable Radio System (AIRS)

[threeofnine]

Several agencies across the state use AIRS Alabama Interoperable Radio System (AIRS) Trunking System, Varies, Alabama. The system is composed of several towers spread out across the state. I am slightly confused as to how the system works. When choosing towers I was recommended to only choose the towers closest to me. Do all the towers act like repeaters or relays, and if so, would this mean that one could listen to an agency 200 miles away or does range from the source still matter?

 

[RaleighGuy]

Several agencies across the state use AIRS Alabama Interoperable Radio System (AIRS) Trunking System, Varies, Alabama. The system is composed of several towers spread out across the state. I am slightly confused as to how the system works. When choosing towers I was recommended to only choose the towers closest to me. Do all the towers act like repeaters or relays, and if so, would this mean that one could listen to an agency 200 miles away or does range from the source still matter?

Each repeater works for a specific area of coverage, as a unit travels across the state it moves from repeater to repeater, it doesn't mean you can hear traffic on all the repeaters from all areas. That said there are exceptions, if an out of area unit is able to affiliate with a local tower you and calls back to his home TG, then you will be able to hear the communications from that TG on your local tower.

 

[TomServo]

I find the way trunked radio systems work pretty fascinating and RaleighGuy's explanation is a good one.

What you'll be able to hear really seems to depend on how much coverage the agency needs. If you're willing to share where you're located, someone in that area might be able to tell you what you could hear.

As an example of how quirky it can be, I'm in central Baldwin County, and can't hear some comms in Orange Beach and Gulf Shores despite both being less than a 14 mile drive from my listening post. The sites in Orange Beach, Gulf Shores and Fort Morgan just don't come in where I am. But at the same time I regularly hear Medstar EMS calls in Escambia County, which is like a 1.5 hour drive away, all off the Seminole tower.

In the summer, it's not unusual for the local towers to start playing some police comms from well outside the area, due to officers bringing their radios with them on beach vacations, ha ha. And if Life Flight from central AL is in the air and down this way I can hear some of their stuff from anywhere from Birmingham to Atlanta or Columbus, which is pretty neat.