Sort of a stupid question about roaming into another trunked systembut?

[cowboywildbill]

What would happen if a car with a trunked radio like State Police or a County unit drove way out of their jurisdiction to another jurisdiction. And that other jurisdiction also had a trunked system let's say both in 800 meg anolog range. And some of the freqs in the two systems were the same in say a ten frq. type II Motorola system I know that the possibility of all of the freqs and or control channels most likely would not be the same, but if the out of State car entered the other system would the cars unit try to comunicate with the other system? Would it search and hit the freqs that are the same? I assume that the tone DPL or PL would be different for those freqs, but would it interfere with the trunked system in the other jurisdiction? Would their computer controler for the system pick it up? I know this is a dumb question, but if someone has to go 600 miles for a prisoner transport or training detail ect. What would happen?
I am under the assumption that the car or portable unit is always transmitting at least in burst every so many seconds to coordinate with the host trunk system. So what happens if it transmits to a foriegn trunk system? Do they know ,or is it not an issue? I was just curious. Thanks and please forgive me if this is the wrong place to post this question.

 

[rescue161]

It would not work. The system ID would prevent the radio from working on another system, even if all of the frequencies were the same.

The radios only transmit a "burst" if they are programmed to auto-affiliate.

 

[cowboywildbill]

Thanks, so then it wouldn't interfere with the other system at all ?

 

[cowboywildbill]

I am asking , because I have roamed outside our system, and it usually says out of range when it loses the trunk system, but I noticed it started scanning in another jurisdiction and wasn't saying out of range. I didn't hear anything but I turned off the unit thinking I might be interfering with someone else. Maybe it was just recieving some of their same freqs signals and that made the out of range message go off the screen. Thanks again.

 

[rescue161]

Thanks, so then it wouldn't interfere with the other system at all ?

Nope. The radio would just display "Out of Range" if it were programmed to do so. Otherwise, it would remain silent and would not interfere with the other system at all.

 

[cowboywildbill]

Thanks you guys are a big help, I'm learning from you. It's time I understood more about what goes on in these systems. Instead of just pushing the mike button. It's kinda like driving a car and not knowing what goes on under the hood. Not that I have to fix any radios. But I am going to get my Ham lic. and start doing some of the easier stuff. I might even buy a couple of the used Motorolas and convert them later after I get my Lic..
Thanks again.

 

[WayneH]

There is a rare possibility that if the sun and moon aligned (i.e., the radio ID, TG, etc were valid) the radio could make a call before it saw the system ID. The SysID is sent every three seconds so when the radio does end up on the wrong system, affiliates, and then realizes it is wrong it sends in an 'oops' message to the CC which in turn generates an event on the CC outbound side stating 'wrong system affiliation' (which is done for administrative tracking purposes).

 

[cowboywildbill]

Does that happen very often ? And does it send a system ID and or also a transmitter ID from the car's unit to their control unit for a log? As many systems as there are some major cities, I would think it would happen.

 

[fmon]

Does that happen very often ?

How often do you see a Solar Eclipse?

 

[WayneH]

And does it send a system ID and or also a transmitter ID from the car's unit to their control unit for a log? As many systems as there are some major cities, I would think it would happen.

No, the SysID is not sent by the mobile unit.

It's very often radios roam on to the wrong system due to RF propagating farther than it needs to (I dealt with an issue like this with a San Diego system a long time ago) but for the radio to make a call is, as I said, very rare to happen because a lot of variables have to be perfect.

 

[cowboywildbill]

I think I understand, but if the radio is programmed to say out of range would it be trying to transmit during that time when that message is displayed ? Or is that displayed when it sees no signal ? And then it would it wait until it recieves it's own Trunk system I.D. to affiliate ? In other words if I understand this correctly it will not transmit until it receives a call from it's origin. This trunking stuff is almost like rocket science to me. I understand Talk Groups and the control channel consept, but it is still amazing to me how all of this works.
And yes I am old enough to have seen a few lunar eclipses ! "Ha Ha" And maybe a solar one too.
Thanks for your time and patience with me about my questions on this subject .

 

[WayneH]

When out of range is shown the radio has attempted to scan the control channel list and found no useful channel within it. It then goes in to a dumb state and won't let you transmit.

Once a radio finds a CC it will immediately attempt to affiliate (if programmed to). It will also verify the correct system ID once it sees it on the CC.

 

[cowboywildbill]

Thanks for clearing that up for me. I wasn't sure how it functioned. I had been under the impression that it transmitted about every three seconds no matter what it saw kinda like a cell phone does looking for a cell site. Now I get the picture. You guy's rock.
Thanks again.