Following IDAS systems with DSDPlus FL

[texas1313]

Hello everyone

I’ve been trying to figure out how to listen to (and follow) IDAS (NXDN) systems using DSDPlus. I’m using the FastLane DSD+ 2.368 with a single RTL-SDR. I have DSDPlus working perfectly tracking multiple P25 Phase 2 systems, Con+, and Cap+ systems. I just cannot get it to track/follow NXDN systems, and have been researching and trying everything possible.

To try to figure it out, I’m focusing on a simple single site NXDN system for a hotel/casino near me (I don’t want to mention the casino name/location), and it is not listed in RR. I looked it up in the FCC database. There are 8 repeater output frequencies. Of those, 5 are decoding as IVAS, 2 are completely silent (monitored for hours), and one is an analog repeater. (Note: I don’t care to listen to this casino, but once I get the IDAS/NXDN following figured out, I can move one to several larger systems in the area that are also stumping me).

The last frequency decodes as Channel 5 and Channel 6, which I’m not clear why yet.

It’s not a super active system, but there is generally someone talking every few minutes thru the day (security, hotel, shuttle, etc).

There is no control channel, so I’m assuming this is a Type D system. None of the licensed frequencies have any control channel data. The data window also shows “Area 0”

I’ve monitored each of the frequencies, and the DSD+ Event log indicates “IVAS ID” and the Channel Activity window lists the channel for each frequency. Over time, I can hear talking on each frequency, and the Channel Activity window displays activity on channels 1 thru 5, with the “Targets” and “Sources” displaying as 1-22, 1-3, 1-96, etc. However, DSD+ is not following any of the traffic, or moving off the single frequency that it’s monitoring (as compared to Cap+ systems where DSD+ searches for activity on the various frequencies).

The scrolling data window display contains information such as (listening on channel 2):

Sync:+IDAS DATA
VCall Group TG=1-5 RID=1-96
SCCH Area=0 Free=1,3


Here’s what my current files look like:

Networks file:

IDAS, 1.1, "XXX Casino"

SiteLoader file:

IDAS, 1.1, 0, "XXX Casino"

Sites file:

IDAS, 1.1, 0, "XXX Casino"


Frequencies file:

IDAS, 1.1, 0, 1, 153.4800, 0.0, 0 ; XXX Casino Ch 1
IDAS, 1.1, 0, 2, 153.1500, 0.0, 0 ; XXX Casino Ch 2
IDAS, 1.1, 0, 3, 152.5500, 0.0, 0 ; XXX Casino Ch 3
IDAS, 1.1, 0, 4, 152.8750, 0.0, 0 ; XXX Casino Ch 4
IDAS, 1.1, 0, 5, 152.3850, 0.0, 0 ; XXX Casino Ch 5
IDAS, 1.1, 0, 6, 152.3850, 0.0, 0 ; XXX Casino Ch 6

(Note: I have Ch 5 and 6 listed with the same frequency, as that that is what DSD decodes on the 5th frequency).

Best audio reception is with 4 kHz bandwidth, and audio is perfect.

All the freqs are within the 2 MHz bandwidth of the RTL-SDR . I’m using the 1R and FMP24-CC batch files, and when I launch 1R and FMP24, I manually enter one of the 5 frequencies and wait for traffic (my frequencies file has over 40 systems, so I start monitoring any particular system by entering one of that system’s control channel or busier frequencies.)

I’ve tried using NEXEDGE48, NEXEDGE96, placeholder network ID’s, but I cannot get DSD+ to follow the voice channels (yes Combined CC/VC monitor is on, voice/data call following is on, etc). It just parks on whatever frequency I enter in the FPM24 window. When someone is talking on that channel, the channel activity window shows what other channels are active, but it doesn’t move off the channel it’s monitoring.

After many days of experimenting, reading other people’s posts on IVAS/NXDN, I’m at a loss. Others have indicated their DSD+ is tracking IVAS NXDN systems, so I’m guessing I’m missing something or possibly have a parameter missing. Obviously this would be easier if there was a control channel.

Any help/advice to figure out how to get the voice following to work would be greatly appreciated! I've tried to include as much data as I thought would be useful.

 

[slicerwizard]

Put the active voice channels in an FMP24 scan list and start scanning in FMP24.

 

[texas1313]

OK.....tried that, with various delays, and of course it stops on an active channel, and the "channel activity" window populates with the activity on the 5 channels at that moment, but then resumes scanning, which clears out the channel activity window, and it does not "follow" the conversation. That just simply scans all the channels, and wouldn't allow me to listen to any particular targets/sources. Thanks for response!

 

[EricCottrell]

Hello,

It might be useful to read this thread.

Understanding IDAS Trunking

Hello, Some useful scribbles as programs decoding IDAS become available. The Icom IDAS Trunk System is an all digital form of an enhanced LTR system. There is no defined control channel and a slow rate data steam (SACH) is used for control information. Much of the same terminology and trunking...

forums.radioreference.com

You can think of IDAS as a digital LTR system. The control channel is a separate low speed data channel from the voice data channel on each frequency.

Like LTR, the frequencies are given repeater numbers. Talkgroups have home repeaters. The example you gave shows me talkgroup 1-5 is on repeater 1. Listening to Channel 1 will result in hearing most of the 1-5 talkgroup's activity. It is know as the home channel for talkgroup 1-5.

Also like LTR, the Free list (Free 1,3) indicates the repeaters that are not active.

If two or more talkgroups with the same home channel are active, then the system will assign one or more other repeaters in the system to the other talkgroups. The home channel will display the activity of all the talkgroups that have it as a home channel.

The home channels should have brief idle bursts when not active. I found they are very brief on single site IDAS systems, so DSD+ may not be able to decode it.

I do not know if DSD+ can track IDAS.

73 Eric

 

[texas1313]

Thank you Eric!

Yes, I had read thru that thread, and was hoping to at least be able to determine the system ID, and was trying things like 1.1

I had also read the thread (1) DSDPlus - Sites/SiteLoader Files & iDAS NXDN - SOLVED/FIXED!! | RadioReference.com Forums, where on Oct 27, 2021, there was discussion that "the Notes.txt and comments for DSDPlus.SiteLoader/DSDPlus.Sites has it wrong and it should be NEXEDGE48 for iDAS Type D systems", and I had been experimenting with various parameters in the Site, SiteLoader, and Frequencies files.

I think you may be right. Everything I've read about DSD+ references the IDAS control channel and looking for Type D SCCH messages during an iDAS CC hunt. The site I'm trying to monitor doesn't have a cc, and behaves more like an LTR system.

After listening to it quite a bit yesterday, and scanning all 5 channels, it appears the 1st channel may be the home for most of the talk groups (I think there are probably 4 or 5, like security, maintenance, housekeeping, parking, etc), and radios go to the next talk group if things get busier.

Each of the 5 channels does transmit a burst every 8-10 seconds, and DSD+ decodes them all fine.

I do have an 436HP scanner, but I don't have the NXDN feature enabled. Since there are a few other larger IDAS NXDN systems in the area (which also don't have a control channel), I may purchase the NXDN feature on my 436HP, using the assumed LCNs from DSD+, and see how that works. I'll probably want to read up more on how Uniden handles such systems. My 436HP already has a full time job .

It seems that there are a lot of LTR systems in the area, so I'm going to just start collecting the data, and eventually put them in to the 436HP and see what happens. Also sounds like a good justification for a new SDS-200.

Thanks again for the quick response and assistance!

 

[slicerwizard]

I had also read the thread (1) DSDPlus - Sites/SiteLoader Files & iDAS NXDN - SOLVED/FIXED!! | RadioReference.com Forums, where on Oct 27, 2021, there was discussion that "the Notes.txt and comments for DSDPlus.SiteLoader/DSDPlus.Sites has it wrong and it should be NEXEDGE48 for iDAS Type D systems", and I had been experimenting with various parameters in the Site, SiteLoader, and Frequencies files.

It should be clear from that thread that the NEXEDGE48 nomenclature advice is bogus.

I don't recall ever seeing in any of the DSD+ help files that iDAS trunk tracking is supported. iDAS doesn't have control channels - it uses home channels, just as LTR does - and DSD+ seems to only trunk track systems that use a single dedicated control channel, or a rotating control channel.