The basic basics of trunking?

[tyler1653]

My curiosity finally got the best of me. I've looked through the database a little for the answers to these simple questions but I couldn't come up with anything right away. I have enjoyed listening to the trunked systems in northern Utah for over 5 years now, but I still don't have a very good idea of how it all works. I understand the concept of trunking in general, but I am still confused by a few things. I live in Davis county, but at random times I will pick up traffic from southern Utah county on the Davis control channel. Sometimes I will be able to listen to a SAR down there, only to have it fade away moments later and leave me hanging. How does that work? Why does some traffic make it's way from county to county while other traffic doesn't? Is there any way to listen to distant traffic all the time by using a nearby control frequency? Another question: what are all of the dozens of control channels in northern Utah used for any way? Many of the ones I can pick up from my house seem to never have traffic on them, except for the ones deemed as "simo" by you all. A simple explanation would finally put my befuddlement to rest. Thanks!

 

[bneilson]

Hey tyler1653

Trunk systems are fairly neat in how they work and link. In the case of UCAN we can get stuff from all over.

I did a presentation in Vegas on Trunking that might help answer some of your questions:
http://video.google.com/videoplay?docid=2933067560876937617&hl=en

The short answer to why you can hear things some time and not others is due to affiliations of users. Basically if a Utah County user is in Davis County their TGs would be repeated in that area. The confusing part is not everybody has "roaming" capability and not all Talk Groups can be on all sites in the system. In addition the system administrators can force any Talk Group to any site at any time. So in some cases you never know what you will hear.

As far as control channels, there is one for each site but there is typically overlapping coverage for sites. This is why you can copy different control channels and each one may be carrying different traffic. From my home I can copy at least 4 sites and each carry different traffic. Depending on what I what to listen to I have to select the appropriate site. In some cases the traffic might be on multiple sites. For example SLCo UHP traffic is always on Site 3 and Site 11, so I could listen to either. But if I am listening to site 15 I will not hear them.

Hope this helps. Watch the video and let us know if you have nay other questions...

 

[N7YUO]

Affiliations: As I travel into Davis County, my cell phone 'affiliates' with a nearby cell tower.
The system knows where to route an incoming call to my phone.
Some, not all, users of the trunked system will also affiliate with other sites as they travel: UHP
Some users are restricted to local sites: Building Inspectors.
Some users have unrestricted access (all sites): Life Flight.
Sometimes a unit will affiliate with a neighboring site because it has the best signal.
Line of sight to local sites may be blocked by terrain, large vehicles, or structures.

You can hear fire dispatches from all over on the SL Simul site 3.
I think is is programmed that way, not just affiliations.
When a major event happens outside of SL County, the state emergency services
would want to know immediately. They could plan to send resources before they are requested.

 

[qlajlu]

The presentation that bneilson put together does a terrific job of explaining what takes place in a trunked system and how affiliation works. You may also want to read the RR Wiki explanation on affiliation written by Lou Maag, the moderator for the Utah Forum.

Note: bneilson, I would encourage you to add your visual presentation to the RR Wiki "Trunking Basics", or at least a link to it since questions about trunking come up so often from so many different quarters. Your visual does present the basics very well and would be easier to understand than the written explanation for many folks. Maybe even a sticky in the Trunking Forum should be considered.

EDITED TO ADD: Oh, and tyler1653, I ask that you to return to your User CP (Left side of second blue bar from top on any page) and provide your location (city & state) in your user profile. That way your location will show in each of your posts automatically and we will not have to guess. We have so many members that we cannot remember where everyone is located and some of our answers to you will depend on your location. It is a small courtesy to the rest of the members.

 

[bneilson]

...Note: bneilson, I would encourage you to add your visual presentation to the RR Wiki "Trunking Basics",...

This has been done...

 

[qlajlu]

This has been done...

Good deal, but I would like to see it placed more prominently on the Wiki page. Right now it is nothing more than a foot note. That is a great video; too great not to be noticed.

 

[ka3jjz]

I think there's a small misunderstanding about the topics on that first page of the wiki. They are not footnotes - they are links. Most all those links lead to articles (or groups of articles, called categories) that discuss that topic. In the case of the trunking link, the very first set of items you see on that article is 'trunking basics'.

bnielson, please feel free to link your presentation to that article. Such information is more than welcome.

73 Mike