In this Capacity Plus system, if you have 3 repeaters for voice and 1 repeater for data, then you have 6 'virtual channels' for voice communications (group calls or private calls). These calls would not affect GPS data, nor should the GPS data affect the voice calls, since the GPS data should be 'offloaded' onto the data-only channel. With that said, I've been working on a MOTOTRBO system in our area (installed by another Motorola dealer) and I found that mobiles/portables were not programmed correctly (among other problems) and were attempting to send GPS data on the 'voice slot' (this is an IP Site Connect system, rather than a trunking system, and they're using 'slot 1' for the 'voice slot'. The mobiles/portables should have been programmed to send GPS data on 'slot 2'. I also found that the GPS/AVL application had been shut down (on the GPS/AVL server) and this caused all of the subscribers to attempt to register, over and over and over again (indefinitely), with the GPS/AVL server that was offline. This is done on the 'voice slot', so this would cause excessive 'channel use' by that 'system', causing more 'busies' on the system for voice traffic.
Another factor that needs to be considered is the 'hang time' of the repeaters in your system. That can be set from 0 seconds to 7 seconds. All repeaters should be programmed the same. There are actually several such 'timers', one for 'overall hangtime', one for Group Calls, one for Private Calls, and one for Emergency Calls. None of those timers can be any longer than the 'overall timer'. So, for example if the Private Call Timer is set to 7 seconds, then the 'overall timer' will be 7 seconds. This means that there will be a 7 second period, after someone unkeys their radio while in a Private Call, during which no one else can access that channel (only those two people in that Private Call). If you have quite a few people doing Private Calls, and that timer is set long, then that could eat up a log of 'air time' on the system, resulting in more 'busies' for others waiting to use the system.
The MOTOTRBO systems are really very different from 'clunky old analog' systems. The only thing common, for the most part, is "RF". MOTOTRBO systems are much more like networked computer systems, with many functions that often interact with each other. So setting up a MOTOTRBO system to operate properly is not really 'simple'. And the System Planner does not cover everything that a person may run into, in working with a MOTOTRBO system. When you add a third-party application (such as GPS/AVL software) to a MOTOTRBO system, then it gets even more complicated to make it work 'right'. But, when they've been set up properly, and they're working 'right', they work great and nothing can beat them, in my opinion.
John Rayfield, Jr. CETma
Rayfield Communications
Thanks Tampa! Yeah, they're greyed out... it just made me nervous. I can't change it since it's grey, I just wanted to make sure that they're not a default rest channel or something goofy like that.
So the real story is this:
We share a test facility and radio system with one of the "big three". I am the admin of the radio system here at the AZ test facility. Recently I got a complaint that the auto company had a 20 minute inability to establish communication on one of the talk groups. I started sniffing around and trying to learn this stuff and stumbled across the screen shots above... Not related to our comm issue, but spooky none the less. Anything federal... I'd rather not deal with 'em.
Since the complaints, I've been in meetings with the old admin and the car guys... maybe someone here can comment:
In studying the motoTRBO system planner guide this is what I think our system is capable of:
With 3 voice repeaters and one data repeater - in capacity plus (all digital) I can support exactly 6 simultaneous voice transmissions. Is my understanding correct?
The other part of the equation is that apparently the auto guys are fond of "private call" sessions. My understanding is that these private calls don't consume more bandwidth than a standard call, but the fact that it's "private" doesn't encourage brevity.
At the end of the day, 3 voice repeaters = 6 voice sessions (private or group calls). Correct?