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Old 05-26-2011, 11:55 AM
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Default Adjacent Sites on P25 Trunked System

What is the meaning of adjacent sites on P25 trunked systems? I noticed some of the DOJ and Military 380MHz systems have adjacent sites associated with them. From a listener perspective, does this mean a radio on the "home" system is capable of accessing talkgroups on a adjacent site?

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Old 05-26-2011, 12:39 PM
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Great Question!

Hopefully other members can add more links or info!


Here some older topics on this...
P25 multisite neighbors

Talks about it on the older Motorola type systems.
http://home.comcast.net/~brerf0x/tru...llprocess.html
http://www.freqofnature.com/SmartZone101.html
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Old 05-26-2011, 8:47 PM
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it is so the radio knows what to listen for when it loses the current tower. this is how they roam between areas. if the adjacent sites were not broadcast over the CC, then every radio would have to have the CC of every tower site programmed in it. and every time a new site was added all radios would have to be reprogrammed.
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Old 05-27-2011, 7:38 AM
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?? ??

Even with the CC Broadcast, the Radio still needs to have ALL the Authorized CC's programed into it to be able to Roam.

If a Radio is Only programmed for 2 CC's then it's stuck on THOSE two CC's forever until re-programmed.

Typically a System MAP has already been created and all the known [in your area for a Extremely LARGE TRS] are programmed into the Radio from the begining.

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it is so the radio knows what to listen for when it loses the current tower. this is how they roam between areas. if the adjacent sites were not broadcast over the CC, then every radio would have to have the CC of every tower site programmed in it. and every time a new site was added all radios would have to be reprogrammed.
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Old 05-27-2011, 6:54 PM
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Even with the CC Broadcast, the Radio still needs to have ALL the Authorized CC's programed into it to be able to Roam.
Not correct. We added a site that wasn't programmed in any existing subscribers, and as soon as it went into wide area trunking, several talkgroups roamed onto that site.

Also, Motorola's XTS/XTL and APX series have an option called "Full Spectrum Control Channel Scan" that is useful where if the radio doesn't find a usable control channel on any of the pre-programmed control channel frequencies, it'll scan the whole band looking for a matching SysID.
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Old 05-28-2011, 9:44 AM
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Interesting, I will have to dig deeper into the Software for that.

However 98% of agencies, I have seen Pre-Program the CC's [28 the last version of some that I have seen] YMMV




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Originally Posted by kf4lhp View Post
Not correct. We added a site that wasn't programmed in any existing subscribers, and as soon as it went into wide area trunking, several talkgroups roamed onto that site.

Also, Motorola's XTS/XTL and APX series have an option called "Full Spectrum Control Channel Scan" that is useful where if the radio doesn't find a usable control channel on any of the pre-programmed control channel frequencies, it'll scan the whole band looking for a matching SysID.
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Old 05-28-2011, 1:12 PM
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yep, MSWIN just added several new towers in my area and not 1 single radio had to be programmed for them since they listen spectrum wide for CC on the system. there ARE a ton of towers preprogrammed in, but not all of them. i've programmed a few hundred APX in the last year, and never had to touch them to add new towers not already in them. the towers broadcasting adjacent CC just speeds up lock to new sites, but FSS will lock pretty quick if the radio has never been turned on close enough to the new site to "know" ahead of time it is there.
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Old 05-30-2011, 12:53 PM
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There is a setting in the CPS to enable full spectrum scan for control channels. This is in addition to adjacent site. Each site will be programmed in the zone controller whether to tell subscribers about it's adjacent sites. There is no programming nessasary in the subscribers. If you use the full spectrum scan feature then your radio can find a system that you don't even have the control channel programmed for. Of course you have to have the system programmed correctly with everything but the control channels. I first discovered the adjacent site feature when I was trying to test a radio that I had programmed. It kept roaming to a nearby site that I did not want it to access. I did not have that site's control channel in the codeplug, but it kept finding the site. I called tech support and was told to check to see how the system was configured. The site was listed as an adjacent site to the one that I wanted and since I was closer to the "unauthorized site" (and actually out of range of the site I wanted) my radio locked on to the wrong site that my talkgroup had no access to. Full bars on signal, but no game. I then changed the system settings to show subscribers that couldn't hit any of thier authorized sites to display out of range instead of a full signal on a site that they aren't authorized to use. SmartZone is fun.
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