Trying to understand...

[N8QGC]

Hi everyone... Just getting back into Police and Fire monitoring. I listened a great deal from the early 80's until about the mid 90's.

As you can imagine it's way different now; kinda like I landed on the moon or something. I've made some interesting observations but am not sure how correct they are.. So I ask the group...

I live in Flat Rock and have the MPSCS programmed as you might expect with the Flat Rock tower control channel. No matter what I do I can't hear anything from Detroit on this frequency. Now when I'm in the city; I work there; if I use the Detroit Control Channel I hear them no problem.

Conversely I hear MSP District 2 Dispatch on both control freqs. So am I to assume that you only hear the traffic on the local tower that is local to the tower with the exception of MSP?

This stuff is crazy....

I had one heck of a time programming my BCD396XT but finally got it figured out. Software programming is a must.

[rdale]

Originally Posted by N8QGC

you only hear the traffic on the local tower that is local to the tower

Correct.

with the exception of MSP?

Incorrect By hearing MSP on both towers, it means an MSP car was in range of each towers when you heard it. Basically since you don't hear Detroit at home, that means no Detroit rigs are in your area.

[n8zcc]

Originally Posted by rdale

Incorrect By hearing MSP on both towers, it means an MSP car was in range of each towers when you heard it. Basically since you don't hear Detroit at home, that means no Detroit rigs are in your area.

I listen to the Southfield tower when I am at work and no surprise, the Southfield tower is only a few miles from Detroit yet I have never heard any Detroit PD or fire off of the Southfield tower. I have heard snow plow traffic from Wayne county off of the Southfiled tower.

How does simulcast traffic propagate to an MPSCS tower? At home, I listen to the Lakeville tower. I can hear Lapeer SO and Macom SO and other agencies and both Lapeer and Macom have simulcast systems.

I would sure like to learn more about how traffic propagate through the MPSCS and simulcast systems.

[N8QGC]

Originally Posted by rdale

Correct.



Incorrect By hearing MSP on both towers, it means an MSP car was in range of each towers when you heard it. Basically since you don't hear Detroit at home, that means no Detroit rigs are in your area.

Strange... I'd really like to learn more about this.. The Traffic I'm hearing on the Flat Rock tower is MSP District 2 Dispatch. It covers a HUGE area.. I've heard cars as far up I-75 from me as the 91 mile marker. Bear in mind I'm at exit 29.

It is very cool to be able to hear them so clearly. Back in the old days when MSP was on 42 MHz you needed one heck of an antenna and some propagtion to accomplish that.

[rdale]

Originally Posted by n8zcc

I listen to the Southfield tower when I am at work and no surprise, the Southfield tower is only a few miles from Detroit yet I have never heard any Detroit PD or fire off of the Southfield tower.

Most of Detroit's talkgroups are confined to Detroit's towers only, so they don't overload neighboring sites.

How does simulcast traffic propagate to an MPSCS tower? At home, I listen to the Lakeville tower. I can hear Lapeer SO and Macom SO and other agencies and both Lapeer and Macom have simulcast systems.

Same as above... That means someone affiliated with Lapeer and Macomb was in range of the Lakeville tower.

Originally Posted by N8QGC

Strange... I'd really like to learn more about this.. The Traffic I'm hearing on the Flat Rock tower is MSP District 2 Dispatch. It covers a HUGE area.. I've heard cars as far up I-75 from me as the 91 mile marker. Bear in mind I'm at exit 29.

That's all part of District 2, so any MSP unit with that talkgroup(channel) selected on their radio will "activate" the closest tower and "draw" that talkgroup to the tower.

[N8QGC]

Thanks for the replies... Very interesting... Not at all the way I thought it might work. Hopefully when I get an outside antenna up at home I can hear Detroit and monitor them from home. Right now I cant.

[drdispatch]

Originally Posted by N8QGC

Strange... I'd really like to learn more about this.. The Traffic I'm hearing on the Flat Rock tower is MSP District 2 Dispatch. It covers a HUGE area.. I've heard cars as far up I-75 from me as the 91 mile marker. Bear in mind I'm at exit 29.

It is very cool to be able to hear them so clearly. Back in the old days when MSP was on 42 MHz you needed one heck of an antenna and some propagtion to accomplish that.

They have also closed several posts & consolidated operations with their regional policing plan. I'm sure it's posted here elsewhere, but here's a map showing the new district boundaries & post locations/numbering. You will also note that Monroe County is now in District 1.

http://michigan.gov/documents/msp/Ne...s_348571_7.pdf

[atfd291]

I've read the posts above, and yes, this has become more of an art form than it was even 10 years ago.

Keep in mind that in a multi-site system, not only are you trunking... but you're also voting. Any radio on MPSCS will try to affiliate with the tower with the strongest signal barring rare exceptions...

Each talkgroup can be "fenced" into one/many/all towers/multicast systems. DPD "Patrol" operations (for example) is "fenced" into the Detroit Simulcast. As rdale so eloquently put it, this is done to keep them from flooding neighboring towers. If a talkgroup is restricted to a tower or multicast, the radio will intelligently try to not vote to stronger towers in which it is not permitted.

So, let's talk about what makes you able to hear a talkgroup on a particular tower/simulcast... You will hear a talkgroup on a tower/simulcast if the following conditions are met:
1.) That talkgroup must be permitted on the tower/simulcast
2.) there is at least one subscriber (radio) affiliated with that tower that has that talkgroup selected
3.) that tower is not having any issues with talking to the zone controller

I hope this helps to de-mystify. If I can be of any other help, feel free to message me.

Disclaimer: This should not be taken as Biblical verse. If I have missed a point either by omission or inaccuracy, please don't hack my post apart.


Thanks!

[N8QGC]

Thanks for the replys fellas... The lightbulb went off! The last post really cleared things up for me. Thanks for helping me out!

[drdispatch]

I think I can speak for all of us when I say "You're very welcome". Atfd291 did a good job of explaining how the system works. It is so far ahead of the 42 Mhz stuff technology-wise; it's mind-boggling sometimes how far we've come. This is not your father's radio. They are now essentially computers that process radio signals.

Welcome back to scanning!

[N8QGC]

Thanks for the "Welcome" and here's to hoping that encryption doesn't shorten my stay! I have read in many forums that it's coming... I'm gonna be majorly bummed if I spent $450.00 to monitor them and now they make it so everyone can't.

I am however; having fun!

[rdale]

Encryption isn't swarming like bees...

[n8zcc]

Originally Posted by atfd291

I've read the posts above, and yes, this has become more of an art form than it was even 10 years ago.

Keep in mind that in a multi-site system, not only are you trunking... but you're also voting. Any radio on MPSCS will try to affiliate with the tower with the strongest signal barring rare exceptions...

Each talkgroup can be "fenced" into one/many/all towers/multicast systems. DPD "Patrol" operations (for example) is "fenced" into the Detroit Simulcast. As rdale so eloquently put it, this is done to keep them from flooding neighboring towers. If a talkgroup is restricted to a tower or multicast, the radio will intelligently try to not vote to stronger towers in which it is not permitted.

So, let's talk about what makes you able to hear a talkgroup on a particular tower/simulcast... You will hear a talkgroup on a tower/simulcast if the following conditions are met:
1.) That talkgroup must be permitted on the tower/simulcast
2.) there is at least one subscriber (radio) affiliated with that tower that has that talkgroup selected
3.) that tower is not having any issues with talking to the zone controller

I hope this helps to de-mystify. If I can be of any other help, feel free to message me.

Disclaimer: This should not be taken as Biblical verse. If I have missed a point either by omission or inaccuracy, please don't hack my post apart.


Thanks!

Yes, definitely de-mystifies but I was thinking given the explanation of the DPD radio traffic staying fenced on their simulcast system. What if a DPD car left the Detroit area, for example the car headed to Bay City. Would the MPSCS system able to route his radio traffic back and on to the Detroit simulcast system?

My observation is the MPSCS system must be complex to program and manage the TGs and the fences.

[rdale]

It depends on the talkgroup he was using. If it was his primary dispatch - maybe. One of their side channels - no. But in any event, any user can access his statewide talkgroup (STATW2 in this case) and use that.

[drdispatch]

There are 3 "levels" if you will, of talkgroups:

Statewide TG's, as rdale said, are meant to be used throughout the state. STATEW1-8, MSP1-8, EMD1-8 are all examples of statewide TG's, along with the G-, H-, & I- EVENT TG's.

Regional TG's are for a certain portion of the state that encompasses several counties, such as D2NORTH, D5K9, D6POST, & so on.

Local TG's are supposed to be restricted to towers adjacent to that area; all of the xxP911, xxCOM, xxSPEV, xxLEIN, etc are not supposed to be used outside a reasonable distance from that county. The NCC (Network Control Center) can enable or disable the ability of local TG's to be used outside their area. There are instances of southern Michigan officers taking their radios up north & listening to their home TG's up there. I don't know if NCC ever turned that feature off.

It is a complex system, but not so bad once you have a basic understanding of how it works. When we first got our training in 2006, I remember the "oooh & ahhh factor" when we were told that a portable in Dundee could talk to a portable in Ishpeming as long as they were on the right TG. After the novelty wore off though, & reality set in, we thought: "Why would they NEED to????".

[rdale]

Originally Posted by drdispatch

I don't know if NCC ever turned that feature off.

No, it still exists at some level. A benefit of living in Lansing is that I hear all the up north P911's during the week when they're here for training