SDRTrunk SDRTrunk - monitoring simulcast

[sean_]

HI All,

Question about monitoring simulcast with SDRTrunk (but should apply the same to op25).

I have control channel 853.900 entered into SDRTrunk and when I play the stream, I receive all kinds of traffic. Some from fire department, some from EMS calling in reports to hospitals, some from bus drivers, some from security for the bus system, etc. Is there a way to isolate to only hear traffic from a specific agency, like EMS or Fire?

Southern Nevada Area Communications Council (SNACC) Trunking System, Las Vegas, Multi-State

Southern Nevada Area Communications Council (SNACC) Trunking System Profile

www.radioreference.com

SDR Dongle
Nooelec RTL-SDR v5 SDR

Thanks for the help!

 

[Whiskey3JMC]

Is there a way to isolate to only hear traffic from a specific agency, like EMS or Fire?

There's no way to hold onto a talkgroup or department as in the scanner sense so you'll need to turn off the "Listen" slider for each talkgroup you don't want to hear

 

[sean_]

There's no way to hold onto a talkgroup or department as in the scanner sense so you'll need to turn off the "Listen" slider for each talkgroup you don't want to hear
View attachment 193509

That makes sense, but I added in only the control channel and still hear all kinds of radio traffic. My alias talkgroup is completely empty.

 

[dave3825]

OP is not showing as a rr subscriber so he most likely does not have that option. He would need to add tg's of interest and then add a blacklist entry.

OP will need addition dongle(s) as 853.900 is present in 4 sites and they all span more than the dongles reach .

 

[sean_]

Actually i am a subscriber (as of last night) but it's under a different email address.

I am able to login to RR on the SDRTrunk and see all the control channels.

 

[sean_]

OP will need addition dongle(s) as 853.900 is present in 4 sites and they all span more than the dongles reach .

Can you say how you found that info? When reviewing the SNACC page, i see 853.900 listed only once:

Southern Nevada Area Communications Council (SNACC) Site: 233 LV Simulcast

Southern Nevada Area Communications Council (SNACC) Site: 233 LV Simulcast Details

www.radioreference.com

 

[dave3825]

I looked at the whole system rather the link you posted.

Take the highest freq listed on the site and minus the lowest freq listed. That will tell you how much the site span is. (4.3625MHz) A rtl sdr dongle will usually cover just over 2 MHz I am not sure what the v 5 actually usable bandwidth is but believe stable is about 2.4 MHz There are settings in SDRT tuners tab with bandwidth choices. Not sure what yours is set to.

 

[sean_]

Understood about the limited bandwidth; thank you for explaining what you looked at to see this.

How does this explain the conversations jumping around so much? Is it because they start talking at 851.000 and the response is on something like 852.500?

And also, if I add in only the control channel (853.900), i hear all kinds of traffic without any talkgroups active in SDRTrunk.

 

[dave3825]

Control channel dictates where voice will occur, known as voice channels. If one has bandwidth on the dongle to cover all the sites freqs, SDRT will tune to the voice channels. If not enough, calls will be missed and not heard. Playlist tells SDRT what you want to listen to. If you imported the system in your rr subscriber account, just turn off listen and record for all tg’s you’re not interested in listening to. Or leave them all set to record, and download and install Trunking Recorder for selective playback of tg’s you interested in. Playback goes thru your browser.

 

[sean_]

Thanks for the info, much appreciated it.

What I'm hearing is traffic almost exclusively from the bus system and I cannot find the talkgroup for that in the radio reference tab of SDRTrunk. There is a drop down with the info in a different area, but no data appears when selected.

What I'll try next is op25 and ensure those talkgroups are not present in the tsv file.

Southern Nevada Area Communications Council (SNACC) TG Category: Regional Transportation Commission

Southern Nevada Area Communications Council (SNACC) TG Category: Regional Transportation Commission Details

www.radioreference.com

 

[dave3825]

What is the tgid of the buses?

Sometimes, depending how the system admins set the system up, not all tg's broadcast on all sites. So one site may or may not carry traffic that other sites do.

 

[sean_]

There's LOTS of them: https://termbin.com/9lbc
40 in total, including maintenance and security.

 

[dave3825]

I am able to login to RR on the SDRTrunk and see all the control channels.

That's in the system view tab.

My alias talkgroup is completely empty.

When you imported the system, I believe you did not import all the tg's in the talkgroup view tab.




Once you import all the talk groups, then you can lock stuff out as then they will be in an alias list.

 

[sean_]

NOW i see my error, of course it's because of your screenshot.

Even though I was looking at the SNACC webpage on RR, i was selecting the wrong system in SDRTrunk! I did try importing the aliases a few times, but nothing ever appeared when traffic was playing, but that's obvious - the talkgroups were not aligning to the traffic that was being transmitted.

I was selecting the p25 system in RR tab of SDRTrunk.

I greatly, greatly appreciate your patience on something so simple to solve.