AFRRCS question

[4791]

I first got a Bearcat scanner, simply to listen to the local aircraft (out of boredom), but I've gradually progressed to a BCD 996P2 as I found I was listening to Forestry and CPKC.

Since then I've downloaded the RR P25 data to my 996P2 and I have started to listen to MV fire dispatch, RV and Airdrie.

I'm slowly trying to get my head around how this system works. I understand that it's mostly encrypted, but what I'm not sure on is... the cell tower I live near in Mountain View has 4 radio channels. Is this the only set of radio frequencies I need to receive for every AFRRCS radio TG?, or are each set of TG's confined to a set of radio frequencies. Would Rocky View FD be on a tower located in RV and MV TG to be scanned on the MV radio frequencies?

Thanks.

 

[kayn1n32008]

my 996P2 and I have started to listen to MV fire dispatch, RV and Airdrie.

You will want to make sure you have all the local sites you can hear, of agencies you want to listen to.

I'm slowly trying to get my head around how this system works. I understand that it's mostly encrypted,

Most law enforcement is encrypted. Some local bylaw/municipal enforcement is as well, some is clear. all RCMP and most AHS is as well. However the 4 AHS Mutual aid talkgroups are in the clear. AHS MA11-AHS MA15 in each zone.

but what I'm not sure on is... the cell tower I live near in Mountain View has 4 radio channels.

AFRRCS Is a wide area P25 trunking system. Each site has a pool of RF channels, and they are dynamically assigned on an as needed basis, either by traffic from other sites, or local users.

Having said that each site ONLY repeats local and network traffic to talkgroups that have users affiliated to the specific site you are monitoring.

Is this the only set of radio frequencies I need to receive for every AFRRCS radio TG?, or are each set of TG's confined to a set of radio frequencies.

No and No.

Most local agencies like fire departments bylaw, municipal enforcement and local government talkgroups that are not encrypted are limited to specific sites as required by AFRRCS rules. But they may not be heard on every local site if there are sites with out radios on those talkgroups.

Would Rocky View FD be on a tower located in RV and MV TG to be scanned on the MV radio frequencies?

Possibly? It depends. If all RV radios are in MV County on a mutual aid call, you may not hear them on RV local sites. It entirely depends if there are radios affiliated to the site. Users at the edges of their counties could roam, register and affiliate to a site outside of their county amd be heard on a site in a different county. There are a huge number of factors that come into play. I am not overly familiar with either RV or MV, how those departments comms are set up, and how they utilize their radios. However, both counties have multiple AFRRCS sites with in the counties.

 

[4791]

So each site has a certain number of frequencies. The one closest to me has three control channels and one that's not.
Do I need to add all three control channels, just one, or even all four ??

 

[kayn1n32008]

So each site has a certain number of frequencies. The one closest to me has three control channels and one that's not.
Do I need to add all three control channels, just one, or even all four ??

I would add all 4 channels

 

[Cortexian]

You need to fundamentally understand how P25 trunking works first.

Every 'RF tower' or 'site' can be built and configured with a certain number of frequencies depending on need. A low traffic site may have 4, a site with more demand/traffic might have 8 - 16 frequencies. More hardware and therefore frequencies are allocated by system admins depending on how much use each site typically sees. Number of frequencies isn't dynamic, it's dependent on the hardware installed at the site.

P25 trunking relies on system control servers that dynamically determine which traffic (talkgroups, private calls, data, etc) is active on a site depending on a number of factors. The biggest factor to be aware of when scanning trunked P25 is that traffic is only sent to a site if there is an active subscriber radio configured to receive it (no point in broadcasting something when no one authorized is listening).

So even though the system is capable of routing traffic to/from almost anywhere in Alberta, you will typically only be able to scan things related to where you actually are. Your scanner doesn't affiliate with or register to a site since it's not a transceiver, so you cannot 'force' a talkgroup to come in to the site you are on. Attempting to force this is exactly what radio system admins HATE, and it's also probably illegal unless you are an authorized user.

Every site has one frequency dedicated to transmitting 'control' data. Every radio affiliated with that site will constantly listen to the control frequency and then respond accordingly. Basically the control frequency just sends out a constant stream of information the radios use to determine what they should do. The control channel will dictate things like "hey radio 12 listening on talkgroup 4050, there's traffic on that talkgroup, I've assigned it to site frequency 4".

You will want to add all the possible control channels, as the system may dynamically change which one is actually broadcasting the control datastream for a variety of reasons. Your scanner will automatically determine which one is sending the control data and 'lock' to it, then it will move to other frequencies automatically as it reads the control information.