Sentinel Departments and Sites

N8827N

Newbie
Joined
Sep 12, 2020
Messages
3
Location
Navarre, FL
Hello,

Is there a way to determine which sites certain departments use? I want to listen to these three county departments but don't want to waste scanning time on the sites below that aren't used by them. Thanks!

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djeplett

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Feb 19, 2005
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Location
NE Wisconsin
Impossible to know for sure. User radios can usually affiliate to any site. You may hear conversations bounce from site to site as a user moves around. Best thing to do is listen for a while and note what site you catch conversations on that interest you and eventually avoid those sites that you don't hear them on.
 

drdispatch

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Feb 17, 2007
Messages
846
Location
Fightin' River, Michigan
Look up the system in the RRDB. Where it lists the sites and frequencies, there is a column for the site name and the county where it is located. If you click on the site name, it will open a page with that site's information, including a small Google Map showing the (approximate) coverage area of that site as a red circle.

As a rule, if you are within that circle, you will be able to receive that site. (Keep in mind the variables of terrain, propagation, weather, external antenna vs. rubber duck, etc.)

As far as which departments use which site, most systems are configured so that if a user's radio is affiliated with a particular site, the traffic on the talkgroup to which that radio is tuned will be carried on that site. There might be a site which covers the county you want to monitor quite well, but if there is another site in an adjacent county which also covers part of your county (and you can receive it), it would be a good idea to scan that site also, lest you miss traffic.
Also, if a site goes down, user radios will affiliate with the next closest site with the best signal.

It will take a little effort, and some geographic knowledge, but it's worth it.
 

N4DJC

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Apr 24, 2019
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Upstate
You might also use location control, if you have a 436/536/SDS, without deleting those sites, it only scans those sites within the range you set.
 

N8827N

Newbie
Joined
Sep 12, 2020
Messages
3
Location
Navarre, FL
Look up the system in the RRDB. Where it lists the sites and frequencies, there is a column for the site name and the county where it is located. If you click on the site name, it will open a page with that site's information, including a small Google Map showing the (approximate) coverage area of that site as a red circle.

As a rule, if you are within that circle, you will be able to receive that site. (Keep in mind the variables of terrain, propagation, weather, external antenna vs. rubber duck, etc.)

As far as which departments use which site, most systems are configured so that if a user's radio is affiliated with a particular site, the traffic on the talkgroup to which that radio is tuned will be carried on that site. There might be a site which covers the county you want to monitor quite well, but if there is another site in an adjacent county which also covers part of your county (and you can receive it), it would be a good idea to scan that site also, lest you miss traffic.
Also, if a site goes down, user radios will affiliate with the next closest site with the best signal.

It will take a little effort, and some geographic knowledge, but it's worth it.
I checked out each site and they're all 12 miles range. So would I be correct to assume I wont receive communications from sites I'm not within 12 miles of? Or put another way, if I'm not located within the the red circle.

That leads me to another question...county wide departments like Santa Rosa Co EMS, Fire, etc. dispatch from a single communications center and their geographic response area runs way beyond the range of any single site. So to ensure coverage, their signal is transmitted from each site site in the trunking system correct? Thanks very much to all.
 

ofd8001

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Louisville, KY
There are three "conditions" possible when it comes to talkgroups and affiliation to sites. One is "preferred", another is "allowed" and the third is denied. All of these are part of the configuration established by the system administrator and they often will hold this information close to their vests. So generally, there are no lists any where that show which talkgroups are associated with which site(s).

Also it is something that administrators can readily change.

The denied condition is where a talkgroup is not allowed to affiliate with a given site. This is typically done to preserve resources for a system. That keeps City "A" radios from affiliating with City "B" site when they are just passing through.

"Preferred" is where a radio, if given a choice, will "try" the preferred site before going to a different site. This is like where you have a city system and a county system which overlap, but can use each other's resources (sites) if needed. "City" radios will first try to affiliate with the "city" site before jumping on to the county site.

"Allowed" means just that, a given talkgroup is permitted to affiliate to a site. Systems may have some talkgroups that are designated "roaming" talkgroups to be used when users travel for official purposes and may need to communicate back home or to other dispatch centers.

This is really a down and dirty explanation. Large area trunked systems are very complex and there are nuances to each.

Best thing to do, is program all the sites you can receive as well as all the talkgroups that you are interested in monitoring. Using logging software can give you some ideas of which talkgroups use which site most often.
 

maus92

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Several overlay sites in this system - not sure why they designed it this way. Maybe for licensing, maybe the "owners" of the freqs wanted to restrict traffic to their system, but allow other to use their resources when necessary. I think you will have to develop your own local knowledge to find out what agencies use what sites - if that is what actually happens. I'll look around for some documentation.
 

n1chu

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Farmington, Connecticut
It’s been mentioned setting the range can help . I always thought it related to GPS. But I could be confusing something else with GPS. It’s that “something“ I hope will Jog your memory and you relate it here...
 

maus92

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I did see that Santa Rosa County and Pensacola host / share their cores with the Escambia County system, which explains the zones. I'd look at only the Santa Rosa based sites, then look where their towers are located. If your listening location is farther than 8 miles from a member tower of any one site, you could lock that site out.
 

drdispatch

Old-Timer
Joined
Feb 17, 2007
Messages
846
Location
Fightin' River, Michigan
I checked out each site and they're all 12 miles range. So would I be correct to assume I wont receive communications from sites I'm not within 12 miles of? Or put another way, if I'm not located within the the red circle.

That leads me to another question...county wide departments like Santa Rosa Co EMS, Fire, etc. dispatch from a single communications center and their geographic response area runs way beyond the range of any single site. So to ensure coverage, their signal is transmitted from each site site in the trunking system correct? Thanks very much to all.
Don't take the range setting in Sentinel too literally; It's somewhat arbitrary. All the sites in my state's trunked system (over 200 sites) are set for the same range in Sentinel, yet there are sites that cover a larger area than that. The range settings in Sentinel are for when location control is used in scanning. The red circles are not entirely accurate either, but they're good as a general idea of a site's coverage area.
 

ofd8001

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Louisville, KY
It’s been mentioned setting the range can help . I always thought it related to GPS. But I could be confusing something else with GPS. It’s that “something“ I hope will Jog your memory and you relate it here...
The Range for sites is a "best estimate" of how far the transmitter will reach. There are many things affecting radio reception. Are you on top of a hill with a good outside antenna or down in a basement on a portable, weather conditions, time of day, other radio systems, etc. just to name a few. When experimenting, I'd double that estimate and then watch the scanner. If you see a signal strength indication for the site, then its good. Otherwise avoid or otherwise turn the site off.

The Scanner or Global Range is something else. It is how far your scanner reaches out in an attempt to monitor something. So if you have a transmitter with a Range of 10 miles and you set your Scanner Range for 20 miles, the scanner will "reach out" 20 miles to see if there are any outer edges inside that 20 mile circle.

It’s been mentioned setting the range can help . I always thought it related to GPS. But I could be confusing something else with GPS. It’s that “something“ I hope will Jog your memory and you relate it here...
The GPS device will send updated location information to a scanner almost continuously. So the beginning point (where your scanner is) is changing as you move. However, how far it is reaching out (global range) remains constant (20 miles in the example). When you use GPS, the Global Range is set to 0, but you can override that.
 

maus92

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Annapolis
I noticed that there are site frequencies missing from the RRDB entry for this system. The Milton site isn't showing its 700 MHz freqs, and the Gulf Breeze site is missing 4 freqs.
 

pb_lonny

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Jul 2, 2012
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Tasmania
It depends on the system / setup. Here we have talkgroups appearing on some sites at times that you then don't hear for ages.
 

N8827N

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Sep 12, 2020
Messages
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Location
Navarre, FL
My range is set to 20 miles so I locked out the sites that are beyond that and it cut down scanning time nicely. I still receive everything I want too. Thanks very much to all for your help.
 

maus92

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Do a submission & they will get added.
That would be inappropriate for me because I am not able to confirm - I can only see what should be there according to the licencing and contract records. Somebody who can actually receive the system over the air needs to verify and submit.
 

nessnet

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Jan 22, 2007
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Eastside of Lake WA
One note on the ranges in Sentinel - some are not for actual sites, but the system.
So, the GPS coordinates (for some) may be for the geographic center of a county for example - NOT the GPS location of the actual transmitter.

If you really want to 'deep dive', try looking up coordinates in Google Earth and seeing if you can find the actual transmitter. Or, looking at the FCC licenses themselves.

Also, if you are actually using a GPS module with your scanner, look into rectangles....
 
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