Bob:
Here is the non tech version
As of right now the jeffco simulcast is a phase 1 9600 baud control channel system . as of right now i dont know of any plans to switch to phase2 for Jefferson county . However shelby county is working on moving to phase 2 . The big major diffrence in phase 1 and phase 2 is with phase 2 you get more bandwith/ channel capacity. But phase 2 is backwards meaning phase 2 radios will work on phase 1 provided that a department is using phase 1 radios . example being say the patrol sgts at a given depatment have a phase 2 radios but the beat guys only have phase 1 one radios . the controller would decode the phase2 signals to phase 1 and vice versa.
simulcast vs (stand alone sites) :
simulcast sytems :
The simulcast system basically is a super repeater. it is brodcasting all the talkgroups from all the simulcast sites only . the signals are basically competing to get broadcast this is how lsm comes into play . lsm is basically to many sites trying to be recieved at on time. Depenping how close you are to the towers you may or may not get lsm .Here at my house i am within 10 air miles of 4 simulcast sites and lsm kills my older scanners. How ever i know people that are not that close and they have no trouble getting simulcast traffic on older equipment.
Stand alone sites:
A stand alone is a site thats not feed back into the simulcast system . I guess you can compare a stand alone to a conventional analog repeater.
The only draw back to this is that they dont broadcast but only a select few talkgroups that are within range .
Here are a few examples of what i mean :
Huffman/ medical center east stand alone site only broadcast jeffco so channel 1 traffic .And other agencies that are in range of it. but you will stiil hear them on the simulcast sites . its possible that when a bessemer so patrol unit was to travel into that coverage area the radio would switch to that tower and broadcast bessemer sheriff's office patrol chanel traffic. This is all done via the system controller automatically. So unless a department physically has their radio set to huffman they would not know what site they are using .
Birmingham fire works the same way. i guess like engine 27 28 29 30. might be set to connect to huffman because they are in the footprint of the tower and you can still here all the traffic from all engines on huffman site . The palmerdale,graysville, warrior and other stand alone towers work the same way. Only broadcasting traffic from departments that have connected to the listed towers .
As for your scanner it works because it has
- APCO-25 Common Air Interface Exclusive and the ablity to decode phase 1 data .
- how ever it will not decode per say a true phase 2 talkgroup only using phase 2 radios, example lets say shelby co so makes the switch to phase 2 and all radios are phase 2 it might not decode it . because the shelby county sites would be broadcasting from true phase 2 equpiment meaning phase 2 radios and controllers.
if anyone wants to add or make corrections to this please feel free to .
hopefully this will help bob
TG 1435 and TG 1437 today.
