Greater Sudbury - Missing certain Tac talkgroups

[mistermightymoose]

Hello,

I live on the eastern side of the Greater City of Sudbury, in Ontario. I'm kind of in a low area (There are two hills on either side of the community). I have a BCD536HP with an external discone antenna that is mounted to the roof of my house.

I'm primarily monitoring the City Fire service without difficulty. The City and Regional dispatches work well and I have no trouble hearing transmissions. The fire service divides their Tac channels by region. The region nearest to me is Tac 5 and I generally don't have any trouble hearing any of these transmissions. It seems that I have trouble hearing other Tac channels. Particularly if a firefighter would be in a building....

I thought that the nature of a trunked radio system meant that all transmissions would be broadcast across the entire system (maybe I'm mistaken). Is there something that I could do to hear these transmissions? Is it possible that they are only using site specific frequencies?

The frequencies can be seen here. Greater Sudbury Trunking System, Sudbury, Ontario - Scanner Frequencies

Thanks!

 

[doctordialtone]

Hello,

I live on the eastern side of the Greater City of Sudbury, in Ontario. I'm kind of in a low area (There are two hills on either side of the community). I have a BCD536HP with an external discone antenna that is mounted to the roof of my house.

I'm primarily monitoring the City Fire service without difficulty. The City and Regional dispatches work well and I have no trouble hearing transmissions. The fire service divides their Tac channels by region. The region nearest to me is Tac 5 and I generally don't have any trouble hearing any of these transmissions. It seems that I have trouble hearing other Tac channels. Particularly if a firefighter would be in a building....

I thought that the nature of a trunked radio system meant that all transmissions would be broadcast across the entire system (maybe I'm mistaken). Is there something that I could do to hear these transmissions? Is it possible that they are only using site specific frequencies?

The frequencies can be seen here. Greater Sudbury Trunking System, Sudbury, Ontario - Scanner Frequencies

Thanks!

Trunking Basics - The RadioReference Wiki

wiki.radioreference.com

See if that helps.

 

[mistermightymoose]

Thanks! So, because there city has different frequencies from different sites a radio could be assigned a frequency that I don't get where I'm located? Or, should I be trying to program all of the frequencies to my nearest site?

 

[chief21]

Modern radio systems can be configured in many ways, depending on the owner's needs and the available resources. The trunked system frequencies are likely used systemwide, but it would not be unusual for certain talkgroups (virtual channels) to be limited only to certain geographic areas/towers, while other talkgroups might always be broadcast systemwide. A talkgroup for a city park, for example, might be limited to only one tower (or perhaps two), since there would be little need to repeat those transmissions across the entire system.

 

[mistermightymoose]

Modern radio systems can be configured in many ways, depending on the owner's needs and the available resources. The trunked system frequencies are likely used systemwide, but it would not be unusual for certain talkgroups (virtual channels) to be limited only to certain geographic areas/towers, while other talkgroups might always be broadcast systemwide. A talkgroup for a city park, for example, might be limited to only one tower (or perhaps two), since there would be little need to repeat those transmissions across the entire system.

If I add the frequencies, somehow, to my local site would they work? I can hear various Tac channels if they are nearby...

 

[mikewazowski]

I thought that the nature of a trunked radio system meant that all transmissions would be broadcast across the entire system (maybe I'm mistaken). Is there something that I could do to hear these transmissions? Is it possible that they are only using site specific frequencies?

Not necessarily. It wouldn't make sense for a call on the east side of the region to be broadcast on a tower on the west side of the region. It would unnecessarily tie up a channel that could be used for something else.

The frequencies can be seen here. Greater Sudbury Trunking System, Sudbury, Ontario - Scanner Frequencies

You've programmed this in as a trunking system right? You're not just entering in the frequencies and scanning them as conventional channels?

 

[mistermightymoose]

Not necessarily. It wouldn't make sense for a call on the east side of the region to be broadcast on a tower on the west side of the region. It would unnecessarily tie up a channel that could be used for something else.


You've programmed this in as a trunking system right? You're not just entering in the frequencies and scanning them as conventional channels?

Yes, it's working as a trunked system.

 

[mikewazowski]

Sounds like they’re just not on the tower you’re monitoring.

 

[mistermightymoose]

If they come near enough I can pick them up.... Is there anyway to verify the system frequencies? If I do a conventional discovery will it give me hits for frequencies that I should be programming?

 

[mikewazowski]

See that’s what confuses me. You’re talking about this system like you’re programming it like a conventional system.

You shouldn’t be hearing them better if they come near you and your scanner gets its frequencies from the control channel so adding in other frequencies won’t help.

If you can share your programming file it might help to understand.

 

[chief21]

According to the RR listing for Greater Sudbury, the trunked system uses unique frequencies for each tower. If you want to hear towers (sites) other than the one you're currently hearing, you'll need to add additional sites to your favorites list. Probably best to add them all and you can turn them each on or off as necessary. Depending on the geographic size of the system, there may be some sites that are just too far away to hear reliably. Once you determine which ones you really need to activate, you can disable the others so that your scanning will be more efficient.

 

[mistermightymoose]

See that’s what confuses me. You’re talking about this system like you’re programming it like a conventional system.

You shouldn’t be hearing them better if they come near you and your scanner gets its frequencies from the control channel so adding in other frequencies won’t help.

If you can share your programming file it might help to understand.

I took the RadioReference database and made a favourite list with only the tower site near my home... I know that all of the talk groups are programmed correctly. If radio keys up near me, I seem to get it (no matter what Tac channel it's on). So, I'm confused as to why I can't hear them across the entire city. Unless they are using frequencies that I don't have programmed?

Just for fun, I ran a conventional discovery between 866.000 and 869.000 MHz. It had several hits with frequencies that are listed in the database and a few that were not listed. I understand that the control channel assigns a frequency, but is it possible that I'm missing some of the Tac channels because I'm missing a control channel? It only seems to be with the Tac talk group...

 

[mciupa]

Is there anyway to verify the system frequencies?

One way would be to do Trunking Discovery on the Sudbury system with a Compare to the Database option.

Do you have the ability to run Unitrunker with an SDR dongle? That should populate a frequency list for you.

 

[slicerwizard]

is it possible that I'm missing some of the Tac channels because I'm missing a control channel? It only seems to be with the Tac talk group...

A trunking system doesn't have Tac channels, so no, it's not possible.

 

[mistermightymoose]

A trunking system doesn't have Tac channels, so no, it's not possible.

I can hear the Tac 5 channel... and it looks like they are part of the trunked system.. ? Greater Sudbury Trunking System, Sudbury, Ontario - Scanner Frequencies

 

[mciupa]

Don't be distracted by that channel comment. We know you mean talkgroup.

I've edited the thread title so we can move past semantics.

 

[chief21]

You're hearing all of the TAC talkgroups "near" you because they're being transmitted from the site (tower) that you're monitoring. When a TAC talkgroup is in use not so close to you, it's likely to be transmitted from a distant site (tower) that you're NOT monitoring. Every tower site in the system you're monitoring uses its own unique set of frequencies. Trunked radios automatically affiliate to only one tower site (usually the closest) and it appears as if the system you're monitoring does not broadcast the TAC talkgroups systemwide. If you want to hear more distant TAC talkgroups, you'll need to add additional sites (probably the most adjacent ones) to your Favorites List.

Each tower site has its own control channel, but all work in conjunction with the system controller. In the case where a TAC talkgroup is in use over a larger area, it might be possible that the users closest to site B would be broadcast over site B (on one of the unique frequencies assigned to that site) and the users closest to site C would be broadcast over site C (on one of the unique frequencies assigned to that site) - but all are hearing the same TAC talkgroup. And - if you are monitoring anything other than sites B or C at the time, you would not hear this talkgroup at all.

When you add additional sites to your Favorites List, your scanner quickly looks at the control channel for site A for any activity, then moves to site B, then site C, etc.. When it sees activity for any of your selected talkgroups, it will automatically switch to the assigned frequency and you will hear the transmission(s). The downside of adding too many sites is that the scanner can only check one site at a time and you could miss important activity on other sites. Clear as mud??

 

[mistermightymoose]

You're hearing all of the TAC talkgroups "near" you because they're being transmitted from the site (tower) that you're monitoring. When a TAC talkgroup is in use not so close to you, it's likely to be transmitted from a distant site (tower) that you're NOT monitoring. Every tower site in the system you're monitoring uses its own unique set of frequencies. Trunked radios automatically affiliate to only one tower site (usually the closest) and it appears as if the system you're monitoring does not broadcast the TAC talkgroups systemwide. If you want to hear more distant TAC talkgroups, you'll need to add additional sites (probably the most adjacent ones) to your Favorites List.

Each tower site has its own control channel, but all work in conjunction with the system controller. In the case where a TAC talkgroup is in use over a larger area, it might be possible that the users closest to site B would be broadcast over site B (on one of the unique frequencies assigned to that site) and the users closest to site C would be broadcast over site C (on one of the unique frequencies assigned to that site) - but all are hearing the same TAC talkgroup. And - if you are monitoring anything other than sites B or C at the time, you would not hear this talkgroup at all.

When you add additional sites to your Favorites List, your scanner quickly looks at the control channel for site A for any activity, then moves to site B, then site C, etc.. When it sees activity for any of your selected talkgroups, it will automatically switch to the assigned frequency and you will hear the transmission(s). The downside of adding too many sites is that the scanner can only check one site at a time and you could miss important activity on other sites. Clear as mud??

Thanks for taking the time to explain. I'll see if adding a few adjacent sites help.

 

[chief21]

Trunking can be a confusing subject. It might help to remember that there is no direct relationship between frequencies and talkgroups. Any talkgroup could be assigned to any system frequency, at any time, depending on the individual site. The ongoing process is dynamic.

 

[mistermightymoose]

One way would be to do Trunking Discovery on the Sudbury system with a Compare to the Database option.

Do you have the ability to run Unitrunker with an SDR dongle? That should populate a frequency list for you.

I tried running Unitrunker. I'm not entirely sure how it works, but I was able to put in the frequency for the control channel and it gave me this list pretty much instantly. This matches up with what is on RR.