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Re: [BCD396XT] Freq -> TGID

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  • Michael R. Howes
    Hey Mike. Let me see if I can explain this without confusing you further.  In the old days, each agency would be assigned a set frequencies for their various
    Message 1 of 11 , Apr 30, 2012
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      Hey Mike.

      Let me see if I can explain this without confusing you further.  In the old days, each agency would be assigned a set frequencies for their various operations.  For instance, Roseville, MI might have 165.100 for the Police dispatch channel , 165.200 for Police car-to-car channel, 165.300 for Events channel, and 165.400 for special emergencies channel (Please Note that channel and frequencies represent different terms).  So lets say that every police agency is set up in a similar way; each having a separate frequency for each of its various operations.  One problem with this is that the frequencies assigned to Events and Special Emergencies may be rarely used.  It is not the most efficient use of radio frequencies.  What trunking does it allows an agency or agencies to share a smaller set of frequencies.    In a trunked system, a central computer assigns these frequencies in real time, based on availability, as each agency goes to
      broadcast.   Let take the example of Roseville, MI.  Lets give them the set of frequencies listed above that were used just by the police department (165.100, 165.200, 165.300, and 165.400).   Now in a trucked system we will share these frequencies with the entire city (Police, fire, maintenance, and parks a rec).  When a radio within any one of these agencies goes to broadcast over a certain channel, the central system looks to see what frequencies are available, and assigns it temporarily to that channel .    For example, Police Squad 1234 keys up his microphone to broadcast over PD dispatch, and the central system assigns PD dispatch 165.100.  All radios that are monitoring the Police Dispatch channel are told that Police Dispatch channel is, at this moment, operating on 165.100.  At the same time, Engine 51 keys up it's microphone to broadcast over Fire Scene1, and the central system assigns Fire Scene1 165.200.   Again all radios
      set to monitor Fire Scene1 are told that Fire Scene1 channel is, at this moment, operating on 165.200  A minute later, Police dispatch channel no longer has traffic, but Fire Scene1 still does.  Maintenance truck 5 goes to broadcast over the Citywide channel.  The central system sees that now 165.100 165.300 and 165.400 are available, but 165.200 is not.  The system then assigns the Citywide Channel the frequency 165.100. All radios that are monitoring the Citywide channel are told that Citywide channel is, at this moment, operating on 165.100. Later Squad 1234 again goes to broadcast on Police Dispatch, but now only 165.400 is available, (all others are being used by other channels). The system assigns 165.400 to Police Dispatch channel, not the frequency it had used earlier (165.100).  This happens over and over again, many times a minute.  In the most simple way this is how trucking works.  



      Now the APCO25 digital trunking system being used in various counties in Michigan (as well as other counties across the U.S.) works in this same way, but on a MUCH larger scale, with each tower site (or grouping) acting as a single trunk system. Each of these county trunk systems acts part larger statewide digital trunk system.  But for now lets concentrate on macomb County.  For Macomb County, there appears to be 2 trunk systems, Macomb Simulcast (Comprised of 9 towers), and Mt Clemens (Comprised of 1 single tower).  Each of these systems (sometimes also called "sites") has a main and back-up control channel.  These the frequencies are used to provide data information about the system, and helps to assign frequencies as they are needed.   866.400 is the main control frequency for the Mt Clemens site.  868.900 is the back up control frequency for that site. The rest of the frequencies listed are the ones used for actual broadcasts, and are
      assigned by the main system via the control frequencies.  Again this is a VERY simplistic representation Trunking, APCO-25 Digital Trunking, and the county of Macomb.  There is much more to it, but lets just stop here for now.  

      I have taken the Macomb County file that I had created and posted on the Yahoo Group site, and have updated it with the Mt Clemens site, as well as Mt Clemens Fire FD info.  The file should already have the needed information for County Sheriff.  Hopefully the addition of the new tower site information will allow you to hear PD traffic for officers operating within the City of Mt Clemens.  I hope this helps you, as well as others.  

      Mike, if you want, we can talk more about this via Skype and/or phone. You can email me directly at mrhowes@....

      To everyone else, If I have made an error here, please let me know.  I have tried to explain this is terms easy to understand, but I don't wish to make things worse by doing it in a way as to be confusing.  

      Thanks to everyone out there, and happy scanning.



      ________________________________
      From: Mike <scannerman@...>
      To: BCD396XT@yahoogroups.com
      Sent: Monday, April 30, 2012 8:38 AM
      Subject: Re: [BCD396XT] Freq -> TGID


       
      Macomb County, Michigan. I am looking for Mt Clemens, the county seat. It
      is patrolled by the Sheriff's Office. I have the Sheriff's Office for the
      rest of the county but I know they are on a different frequency in Mt
      Clemens. The frequency I found on RadioReference.com is 866.40000.

      Thank you. I love this scanner but it is long learning curve. Been reading
      the (easy to read) manual but it is a lot to digest quickly!

      Mike

      --------------------------------------------------
      From: "MCH" <mch@...>
      Sent: Sunday, April 29, 2012 7:15 PM
      To: <BCD396XT@yahoogroups.com>
      Subject: Re: [BCD396XT] Freq -> TGID

      > OK. Let's start with where you are (State and County). Where are you?
      >
      > Joe M.
      >
      > Mike wrote:
      >> I could not find it. Part of the problem is that I do not fully
      >> understand
      >> how trunked versus conventional systems are entered. I'm still reading
      >> the
      >> manual and trying to learn. So it may be my fault that I cannot figure
      >> out
      >> the translation!
      >>
      >> Mike
      >>
      >>
      >> --------------------------------------------------
      >> From: "MCH" <mch@...>
      >> Sent: Sunday, April 29, 2012 2:55 PM
      >> To: <BCD396XT@yahoogroups.com>
      >> Subject: Re: [BCD396XT] Freq -> TGID
      >>
      >>> Radioreference.com likely has the info.
      >>>
      >>> Joe M.
      >>>
      >>> Mike wrote:
      >>>> I searched the archives but could not find an answer. Zero search
      >>>> results, maybe did not use correct wording.
      >>>>
      >>>> I have the frequency for Mt Clemens, Michigan (866.40000) but do not
      >>>> have
      >>>> a TGID. If I have a frequency, how can I find the TGID so I can listen
      >>>> to
      >>>> the talkgroups?
      >>>>
      >>>> Thanks in advance.
      >>>>
      >>>> Mike
      >>>>
      >>>>
      >>>> [Non-text portions of this message have been removed]
      >>>>
      >>>>
      >>>>
      >>>> ------------------------------------
      >>>>
      >>>> Yahoo! Groups Links
      >>>>
      >>>>
      >>>>
      >>>>
      >>>> ----------------------------------------------------------
      >>>>
      >>>>
      >>>> No virus found in this incoming message.
      >>>> Checked by AVG - www.avg.com
      >>>> Version: 9.0.930 / Virus Database: 2410.1.1/4966 - Release Date:
      >>>> 04/29/12
      >>>> 02:34:00
      >>>>
      >>>
      >>> ------------------------------------
      >>>
      >>> Yahoo! Groups Links
      >>>
      >>>
      >>>
      >>>
      >>
      >>
      >> ------------------------------------
      >>
      >> Yahoo! Groups Links
      >>
      >>
      >>
      >>
      >> ----------------------------------------------------------
      >>
      >>
      >> No virus found in this incoming message.
      >> Checked by AVG - www.avg.com
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      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
      >



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