Question about apco 25 systems

[beaujo_fire]

I have a question regarding apco 25 9600 baud systems. When a radio, say a xts type radio is programmed for a smartzone multi tower 800mhz trunked system. And the radio is turned on and has a channel selected and say 8 channels in it scan list and is in the scan mode. I am guessing that when the radio is turned on, it affilates on a nearby tower and it affilates only on the talkgroup in which the radio is selected. Is that correct. I am also assuming that the radio will only hear communcitions that are on one of the channels in its scan list if there is a radio affilated on that talkgroup (the one that is in radio 1's scan list) on that same tower. Hopefully what I am saying is making since. So basically a xts or astro spectra or whatever it may be affilates only on it selected talkgroup and the rest of the channels in it scan list only act as a scanner and only hear communications on the scan list channels if other radios are affilated on the same tower and are talking on that group. Just like a scanner monitors communications. Is that correct.

My reason for asking is, that when out of the area of my home area, the radio if placed in scan mode, with the scan list of my home area, will only recieve communications that occur on the selected channel. Even when scanning, so that led me to believe that the radio acts only as a scanner for the scan list and affiliates only the selected talkgroup.

Am I on the right track in understanding how this trunked apco 25 system works.

Thanks for any and all help.

Dave

[jcobb]

Simply put - yes, you are correct. That's why we don't put scan in our system radios.




Jack

[Pj]

To go one step further, you cannot do a "safety scan" on the 9600 systems. On a radio flashed for the 9600 control channel, the radio will auto-affiate to the system (if you can even fangle the new style system key), there are no choices. Setting the radio to Smartzone will also do the same thing on 3600 systems. The option for Affiate on PTT is not an option on the Astro series (it was in the Jedi series radios).

So in short, you CANNOT use an Astro radio as a scanner on a true APCO25 trunked system (9600cc) unless you have the System key (different from the 3600cc systems) AND a valid radio ID from the system admin.

Pretty much you have to use one of the Radio Shack or Uniden scanners to monitor these systems.

[beaujo_fire]

Ok, that is how I thought it worked. I am not asking so that I can make a xts radio into a scanner. I was just asking so that I understood how smartzone 9600 baud systems worked in scan mode. That is all.

And as for the system key. The same key generator program will make a system key for an 9600 astro system. Just like it does for the analog 3600 system. The software to make that key is no different.

thanks for the info.

Dave

[mancow]

Simply put - yes, you are correct. That's why we don't put scan in our system radios.




Jack

IT LIVES!!!!




It's about time you started posting again.

[RKG]

I'm not entirely clear on what the question is, but I offer the following:

1. Affiliation is not a "per talkgroup" concept, but a "per system" concept. When your radio is turned on, it attempts to locate a control channel with the correct SysID; if it finds one, it quickly checks the control channels for the adjacent "zones" (which are encoded in the marker stream) for a better signal, and when satisfied, it sits on the control channel reading the marker stream for OSWs.

2. Assuming your scan list is limited to TGs on the same system (i.e., "Priority Monitor" for the scan type), the radio doesn't "scan" anything in the sense in which we became accustomed to it with conventional radios. Rather, it waits for a OSW commanding a voice channel assignment for a TG in its list and it executes that command, switches to the voice channel, and listens to the talk. When the disconnect command is received, it goes back to control channel and waits some more.

3. A feature of SmartNet II is that data concerning what TGs are currently the subject of active channel grants is also available over the voice channel while your radio is listening to a voice channel. If you have not set a priority scan mode, this data is ignored. If you have, and if while listening to a voice channel assigned to an active conversation on what is a non-priority TG in your scan list, and your radio then detects that a channel grant has been made on a priority TG in your scan list, the radio will jump to the voice channel for that assignment.

[xmo]

When the radio affiliates it does tell the Zone Controller what its currently selected talkgroup is. This is necessary so that the ZC can make appropriate decisions about channel assignment and routing of call audio to sites with active radios on particular talkgroups.

As the original post surmised, this process does not extend to an individual radio informing the ZC which talkgroups are in its active scan list - so yes - if there is traffic for a talkgroup in your list and there is no radio affiliated on that talkgroup on that site - you won't hear it because that call will never get an assigment in that sites OSW.

[beaujo_fire]

Thanks for the replies. I thought that was how the systems worked as I didn't think that when the radio affiliated it sent all the scan list info.

Thanks for the help

Dave