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MobileTech NXDN Network

k2hz

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#21
And now I found R13-26 Baker Hill WQYK725 150.965

NL:328-13 32 60 73 77

R99328-13 CC=528
R328-13 CC=792
R136-13 CC=776

It is also an Idle CC at this time.
 

k2hz

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#23
There is obviously a wealth of good information about the system and adjacent sites CC frequencies buried in CC data stream but, at least in the form DSD+ decodes it, there seems to be no rhyme or reason to the numbers.

The basic NL numbers do correspond to the Mobiletech LTR-NET sites so that helps but the detailed site neighbor info in the data stream seems to make no sense nor do the CHIDs displayed for voice activity.

NEXEDGE48 is supposed to be a direct frequency access vs LCN based system so these numbers must match some standard band plan but I can't see how.

I am going to be doing more analysis of the new sites today to see if I can catch activity to identify other site frequencies. The previously identified Bristol site is fairly busy with the Greece CSD school buses a major user and S Seneca CSD, a former LTR-NET user, is also on there.
 

k2hz

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#24
The RRDB has been updated with the new sites.

I have been monitoring Site 60 and it is operating in both NXDN and LTR mode. The normal LTR CC remains in service and the active NXDN CC takes one of the available LCNs which is busied out on the LTR side and the voice traffic from either side seems to share available frequencies.

The NXDN CC at most sites seems to rotate daily between 2 frequencies.

I have confirmed that DSD+ shows 150.905 as CH159 when used for voice traffic at sites 60 and 73 and
153.1025 shows as CH165 when active for voice at Site 32.
 

k2hz

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#25
I have some more sites added to the RRDB.

The Channel IDs are in the range 159-166 so far and do not seem to fit a standard band plan. There have been comments in other Forums that this is an issue with VHF NEXEDGE48 systems vs standard band plans for UHF.

The odd Site IDs and Channel IDs that DSD+ is reporting in the log and main windows seem to be a problem with the way they are handling the ADJ_SITE_INFO data for this system. I am working on documenting the problem and will contact the DSD+ developer.
 

GTR8000

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BEE00
#26
After k2hz and I turned our brains into mush trying to figure this all out over the past two weeks, it finally reached a successful outcome!

Turns out that DSD+ was not decoding these NEXEDGE Gen2 DFA (Direct Frequency Assignment) systems correctly, and was therefore spitting out some nonsensical data.

It had absolutely nothing to do with "bad decoding/poor signal or interference or other bad audio parameters", or incorrect switches in the DSD+ command line, or anything of the sort.

No, in fact it turned out to indeed be the software, not k2hz's setup. Actually it was thanks to k2hz taking the time to work this out with me, and his submission of some good raw control channel audio, which led to the DSD+ author making the necessary fixes in FL 2.155 to support these DFA systems.

Dick, a pleasure working with you, as always! :D
 

k2hz

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#27
Some submissions from the Syracuse area to fill in the details for the eastern end of the system would be very helpful..

My reception of Niles and Tully is broken up by co-channel Mobiletech LTR-NET activity from nearby sites. Oswego and Manlius are too weak to decode at my location. Neighbor lists from these sites may reveal additional sites.

DSD+ 2.155 gives detailed site and neighbor frequency information from CC data.

Some site frequencies are being shared between the NXDN and LTR-NET system. The LTR-NET CCs are remaining but other LTR-NET site frequencies are alternately used for NXDN. It appears that the active NXDN CC frequency is busied out on LTR and the voice channels alternate between the two systems. Additional new site frequencies are dedicated to NXDN.

The NXDN CCs may rotate, seemingly at random times.
 

k2hz

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#28
I found a minor glitch in DSD+ 2.155 that truncates the displayed frequencies to 2 or 3 decimal places vs the proper 4 under certain circumstances. I have documented this to the developers along with a correlation to when it occurs so I expect it will be resolved in a later release.

It is not a major problem but a frequency like 153.0425 may show up as 153.04 on the DSD+ log displays.
 

k2hz

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#29
In case anyone is still interested in this system- The latest DSD+ Fast Lane release has cleared up all the bugs with Nexedge48.
There are some recent signs of growth in the system with some additional frequencies added at existing sites.
There is a new Site 35, Seneca, just becoming active on digital with the former LTR-NET CC, 151.970, now Nexedge48, RAN 35. I am seeing some additional TGs active but not on my local sites so I don't have positive IDs to submit yet. Probably more school bus systems.
 

k2hz

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#30
In case anyone is still interested in this system- The latest DSD+ Fast Lane release has cleared up all the bugs with Nexedge48.
There are some recent signs of growth in the system with some additional frequencies added at existing sites.
There is a new Site 35, Seneca, just becoming active on digital with the former LTR-NET CC, 151.970, now Nexedge48, RAN 35. I am seeing some additional TGs active but not on my local sites so I don't have positive IDs to submit yet. Probably more school bus systems.
The system is expanding. New sites 8 & 43 on the air in the Corning area. I am keeping the RRDB updated as new system info is discovered.
 

JRBarrett

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#32
A quick intro, since this is my very first post on the forums.

I have been involved in radio communications for most of my life, both as a hobby and professionally. I worked in LMR from 1982 to 1993, first at the Motorola MSS in Elmira, and when that company imploded due to infighting between the owner and her children, I continued at an independent shop. (This was all in the pre-trunking, pre-digital era). During that time I worked on most of the public safety systems in Steuben, Schuyler, and Chemung counties in New York, and Bradford and Tioga counties in PA. Many of those systems have changed quite a bit in the intervening years, while others have not changed at all.

I then spent several years as a broadcast engineer in local radio and television. Since 2005, I have been working exclusively in aviation, specializing in avionics. I currently employed in the corporate flight department of a certain Fortune 500 company based near here...

Though I have been a long-time Ham, I have always been primarily active on HF. I have recently gotten back into scanning VHF/UHF.

As to the topic at hand: I have been monitoring the local Mobiletech NXDN CC in Horseheads (Site 43) with DSD+ Fast Lane version 2.169, coupled to an RSP1A SDR.

The decode shows that the site 43 CC is receiving on 159.765

The NL shows site 8 (Corning), site 21 (Ithaca), site 35 (Seneca), site 41 (Penn Yan) and Site 42 (Dansville). The frequencies all correspond to those listed in the RRDB for those sites, and they are indeed all geographically the nearest to here.

The final “mystery” site in the NL shows: R13-69; CC=40664 150.83

There is no site 69 in the current DB. 150.83 is listed as a Mobiletech NXDN CC for site 73 in Newark in Wayne county. It is also shown as an analog channel in the older LTR Net system in Prattsburgh in Steuben county. That location would make more sense in the NL as it is much closer to here than Newark, so perhaps the Prattsburgh LTR site is transitioning to NXDN

The Corning CC on 150.9425 shows it receives on 159.735. Its NL shows: 21, 32, 41, 42, 43 and the “mystery guest” - site 69.
 

k2hz

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#33
Good work on analyzing the DSD+ data!. It is a valuable tool for this system now that the earlier bugs have been resolved. The DSD+ developer has been great on responding to my bug reports.

Regarding Site 69 - It can not be Prattsburgh since that is site 63. Mobiletech has been consistent in site numbers between the legacy LTR-NET and the new NXDN system. FCC data shows 160.830 is WQUZ417, Barton, Tioga County for Mobiletech with NXDN emission so that would be the prime suspect. It is not an LTR-NET site so it very possibly could be site 69.

I am out of range for decode of Corning and Horseheads. I submitted the CCs to the RRDB based on neighbor list data. I can detect very weak NXDN signals but too weak for decode to get the detailed site data. It would be very helpful if you submit the voice channel frequencies for these sites to the RRDB.

A major problem with monitoring is the co-channel reuse at area sites, particularly if there is a LTR-NET CC on the channel in the area. This is why I was originally getting poor decodes on some area CCs. I found there was a constant co-channel LTR CC carrier from another site interfering with the digital data. In other cases, the LTR voice channel idle pulses break up the NXDN data.

Voice channels on a site may alternate between LTR and NXDN. I first became aware of the digital implementation from monitoring the LTR-NET Avon site for the LA&L RR. I noticed bursts of digital "tailgating" TG voice activity on the site and occasional co-channel digital interference from Newark on the shared 150.905 channel. The LTR-NET CCs seem to remain constant as listed in the RRDB but the NXDN CCs do shift on an apparent random basis. That is why more than one CC is listed for most NXDN sites.
 

k2hz

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#34
There is a minor bug with 1.69 sometimes not displaying some or all neighbor list data. It is due to Mobiltech indicating 8 neighbors but only broadcasting data for 7 in some cases. This caused confusion for DSD+ in what was displayed in the Event Log screen. This was promptly fixed in a 1.70 version which I believe is a Beta but the fix will probably be in the next Fast Lane release.

I suspect the sometimes discrepancy between Mobiltech "advertised" number of NL sites and the actual number of site's data broadcast is a temporary situation as the system is being built out. In any event, DSD+ is now dealing with it and displaying all available data.

What caused me some confusion was with the DSD+ interpretation of NXDN CAI 6.5.38 Adjacent Site Option. The "Site Number" is defined as "No. of Adjacent Sites" where allowable values are "Site No. 1 to Site No. 15"

The DSD+ interpretation as an incrementing "3 Neighbors", "5 Neighbors" etc.. in the console data display as each neighbor site data appeared implies that this is a cumulative count of sites rather than a number assigned to each site designating its position in the neighbor list. I don't know if this number is arbitrary or implies a priority but that in not relevant for now. It appears that the correct interpretation of this data should be "Neighbor 3", "Neighbor 5" etc.. to avoid confusion.
 

JRBarrett

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#35
Good work on analyzing the DSD+ data!. It is a valuable tool for this system now that the earlier bugs have been resolved. The DSD+ developer has been great on responding to my bug reports.

Regarding Site 69 - It can not be Prattsburgh since that is site 63. Mobiletech has been consistent in site numbers between the legacy LTR-NET and the new NXDN system. FCC data shows 160.830 is WQUZ417, Barton, Tioga County for Mobiletech with NXDN emission so that would be the prime suspect. It is not an LTR-NET site so it very possibly could be site 69.

I am out of range for decode of Corning and Horseheads. I submitted the CCs to the RRDB based on neighbor list data. I can detect very weak NXDN signals but too weak for decode to get the detailed site data. It would be very helpful if you submit the voice channel frequencies for these sites to the RRDB.

A major problem with monitoring is the co-channel reuse at area sites, particularly if there is a LTR-NET CC on the channel in the area. This is why I was originally getting poor decodes on some area CCs. I found there was a constant co-channel LTR CC carrier from another site interfering with the digital data. In other cases, the LTR voice channel idle pulses break up the NXDN data.

Voice channels on a site may alternate between LTR and NXDN. I first became aware of the digital implementation from monitoring the LTR-NET Avon site for the LA&L RR. I noticed bursts of digital "tailgating" TG voice activity on the site and occasional co-channel digital interference from Newark on the shared 150.905 channel. The LTR-NET CCs seem to remain constant as listed in the RRDB but the NXDN CCs do shift on an apparent random basis. That is why more than one CC is listed for most NXDN sites.
I haven’t seen any voice channel decodes on the Horseheads CC yet, but will keep monitoring. My signal quality from that site is excellent. The tower is about two miles line-of-sight.

The nice thing about using the RSP1A SDR to look at the band is that I can see at a glance the relative signal strengths of the various CCs for this and other systems, and any potential interference. The Corning site is about half the amplitude of the Horseheads site on the display at my house. I can see the Ithaca CC, but it is too weak to decode from my location here in the valley.

Jim Barrett
 

w2csx

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Rochester,NY & Charlton,MA
#36
Good work on analyzing the DSD+ data!. It is a valuable tool for this system now that the earlier bugs have been resolved. The DSD+ developer has been great on responding to my bug reports.

Regarding Site 69 - It can not be Prattsburgh since that is site 63. Mobiletech has been consistent in site numbers between the legacy LTR-NET and the new NXDN system. FCC data shows 160.830 is WQUZ417, Barton, Tioga County for Mobiletech with NXDN emission so that would be the prime suspect. It is not an LTR-NET site so it very possibly could be site 69.

I am out of range for decode of Corning and Horseheads. I submitted the CCs to the RRDB based on neighbor list data. I can detect very weak NXDN signals but too weak for decode to get the detailed site data. It would be very helpful if you submit the voice channel frequencies for these sites to the RRDB.

A major problem with monitoring is the co-channel reuse at area sites, particularly if there is a LTR-NET CC on the channel in the area. This is why I was originally getting poor decodes on some area CCs. I found there was a constant co-channel LTR CC carrier from another site interfering with the digital data. In other cases, the LTR voice channel idle pulses break up the NXDN data.

Voice channels on a site may alternate between LTR and NXDN. I first became aware of the digital implementation from monitoring the LTR-NET Avon site for the LA&L RR. I noticed bursts of digital "tailgating" TG voice activity on the site and occasional co-channel digital interference from Newark on the shared 150.905 channel. The LTR-NET CCs seem to remain constant as listed in the RRDB but the NXDN CCs do shift on an apparent random basis. That is why more than one CC is listed for most NXDN sites.
I find that interesting that WQUZ417 would be 160.830,cause that is AAR Ch 72 for railroad and since it's in Tioga,wondering if Norfolk Southern is going to use that?
 

k2hz

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#38
I haven’t seen any voice channel decodes on the Horseheads CC yet, but will keep monitoring. My signal quality from that site is excellent. The tower is about two miles line-of-sight.

The nice thing about using the RSP1A SDR to look at the band is that I can see at a glance the relative signal strengths of the various CCs for this and other systems, and any potential interference. The Corning site is about half the amplitude of the Horseheads site on the display at my house. I can see the Ithaca CC, but it is too weak to decode from my location here in the valley.

Jim Barrett
Most Mobiltech activity tends to be school buses so early morning and mid afternoon tend to be the busy times. None of their NXDN customers seem to be very active nights or weekends.

Can you see the 150.830 Site 69 CC?
 

JRBarrett

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#39
Most Mobiltech activity tends to be school buses so early morning and mid afternoon tend to be the busy times. None of their NXDN customers seem to be very active nights or weekends.

Can you see the 150.830 Site 69 CC?
I don’t see anything on 150.830, but if the site is indeed in Barton, it would probably be blocked by the hills on the east side of Elmira. I’m planning to install SDR Console and DSD+ on a Windows laptop, so I can drive up to a hilltop with the RSP1 SDR. I can probably see the new site on 150.830 from up there if it is indeed on the air. Might even be able to get a directional bearing. (Need to borrow a 2 Meter Yagi from a friend.)

I discovered that the laptop battery is dead, so have ordered a new one.

I had the same thought about most of the Mobiletech clientele being primarily weekday operations. None of the school bus systems in the current NXDN talk group list in the RRDB are anywhere close to here, but I see many local companies are listed in the LTR Net talk groups list - including Corning, Addison and Bath school buses, and Casella Waste Systems. If any of those have transitioned to NXDN, I should see some activity.
 
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