New DART Radio System

mwjones

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Site 87.87 mystery solved - as I suspected it is DFW.

I had the day off work today and went to Founder's Plaza, and I could just barely pick up the control channel - I could see it on the DSDPlus "scope" but it was too weak to decode, so a quick trip down the service road to a turnaround and back North saw the signal pegged the scope as I approached the above shelter with Yagi's.

Code:
    Site: 87.87  NAC=057    ; DFW Airport 700MHz

    Neighbor: 46F74.0D6-50.50    ; North Simulcast 700MHz
    Neighbor: 46F74.0D6-60.60    ; North Simulcast
    Neighbor: 46F74.0D6-70.70    ; South Simulcast 700MHz
    Neighbor: 46F74.0D6-78.78    ; Downtown-South Simulcast
    Neighbor: 46F74.0D6-89.89    ; DFW Airport
    Neighbor: 46F74.0D6-91.91    ; Mockingbird Tunnel 700MHz
    Neighbor: 46F74.0D6-93.93    ; Mockingbird Tunnel
    Neighbor: 46F74.0D6-95.95    ; Hurst

    Channel 9-860:    771.69375-1      SCC
    Channel 1-824:    774.15625    CC
    Channel 9-1648:   774.15625-1  CC

Now, this presents an interesting result - As you'll notice the CC is listed twice, and both one of the CC entries and the SCC entry has a "-1" behind the frequency. I had to pull the logs to confirm and compare with a log I captured last year in Oklahoma.

2024/11/15 14:45:04 Freq=774.156250 NAC=057 FM demodulated P25p2 PSK signal detected; forcing P25p2 PSK demodulation

This site is using a Phase II (TDMA) control channel - Harris is the only vendor to currently support it on the hardware side, and there's no scanner on the market today that can decode it - and even in SDR receivers, only a few pieces of software can decode it (in my case DSDPlus.) Phase II control channels are still pretty rare (the only other time I've seen it is on American Electric Power's system up in Oklahoma and North-East Texas - which is why I had to go look at the old logs), so this is a first for the D/FW area.

There are only two frequencies on the 700MHz band licensed at the airport site, compared to the 5 800MHz frequencies - so going to a TDMA control channel gives them 3 concurrent TDMA Voice talkpaths, or 1 CDMA Data talkpath concurrent with 1 Voice talkpath on the 700MHz band, further increasing efficiency of the system.

Now to go and write the submission that hopefully makes sense to the RRDB admins.
 

BenScan

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Site 87.87 mystery solved - as I suspected it is DFW.

I had the day off work today and went to Founder's Plaza, and I could just barely pick up the control channel - I could see it on the DSDPlus "scope" but it was too weak to decode, so a quick trip down the service road to a turnaround and back North saw the signal pegged the scope as I approached the above shelter with Yagi's.

Code:
    Site: 87.87  NAC=057    ; DFW Airport 700MHz

    Neighbor: 46F74.0D6-50.50    ; North Simulcast 700MHz
    Neighbor: 46F74.0D6-60.60    ; North Simulcast
    Neighbor: 46F74.0D6-70.70    ; South Simulcast 700MHz
    Neighbor: 46F74.0D6-78.78    ; Downtown-South Simulcast
    Neighbor: 46F74.0D6-89.89    ; DFW Airport
    Neighbor: 46F74.0D6-91.91    ; Mockingbird Tunnel 700MHz
    Neighbor: 46F74.0D6-93.93    ; Mockingbird Tunnel
    Neighbor: 46F74.0D6-95.95    ; Hurst

    Channel 9-860:    771.69375-1      SCC
    Channel 1-824:    774.15625    CC
    Channel 9-1648:   774.15625-1  CC

Now, this presents an interesting result - As you'll notice the CC is listed twice, and both one of the CC entries and the SCC entry has a "-1" behind the frequency. I had to pull the logs to confirm and compare with a log I captured last year in Oklahoma.



This site is using a Phase II (TDMA) control channel - Harris is the only vendor to currently support it on the hardware side, and there's no scanner on the market today that can decode it - and even in SDR receivers, only a few pieces of software can decode it (in my case DSDPlus.) Phase II control channels are still pretty rare (the only other time I've seen it is on American Electric Power's system up in Oklahoma and North-East Texas - which is why I had to go look at the old logs), so this is a first for the D/FW area.

There are only two frequencies on the 700MHz band licensed at the airport site, compared to the 5 800MHz frequencies - so going to a TDMA control channel gives them 3 concurrent TDMA Voice talkpaths, or 1 CDMA Data talkpath concurrent with 1 Voice talkpath on the 700MHz band, further increasing efficiency of the system.

Now to go and write the submission that hopefully makes sense to the RRDB admins.
Ugh! The laptop I took last week didn't have the newest version of SDRTrunk with P2 TDMA control channel support, and I guess the Unications aren't there yet either. Thanks!
 

BenScan

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Looks like DART Police have moved to encrypted talkgroups.
 

andy51edge

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Adjacent to this thread, today I observed the Silver Line testing, the train ops were off the system and instead on AAR channel 44, 160.770 MHz. The new trains looked great. PXL_20241210_182709914 small.jpg
 

KenFL9

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Adjacent to this thread, today I observed the Silver Line testing, the train ops were off the system and instead on AAR channel 44, 160.770 MHz. The new trains looked great. View attachment 174197
160.770 will be the primary channel for train operations on the DART Silver Line to fit in with the existing VHF analog carrier squelch systems in use by TEXRail (160.950) and Trinity Railway Express (161.040).
 

andy51edge

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160.770 will be the primary channel for train operations on the DART Silver Line to fit in with the existing VHF analog carrier squelch systems in use by TEXRail (160.950) and Trinity Railway Express (161.040).

I agree. They will still carry freight trains (of varying frequencies) on the Silver Line just like TEXRail and TRE. Plus the Silver Line will share it's ROW from the airport 'till DFW Airport North Station. Makes perfect sense.
 

mwjones

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Anybody else heard announcements on 11043 or 11046?
Not those specific groups, but I logged a similar platform announcement on 11004 back on March 1st.

My guess is the 11xxx talkgroups all represent individual stations on the DART lines, and the Dispatcher can key up and make an announcement to any station remotely (in addition to maybe a simplex input for someone at the station to key up and make announcements).

I've logged radio affiliations to 33 talkgroups between 11000 to 11099 but only that single transmission. According to DART there are 65 stations on the system (presumably not counting the 10 new stations on the under-construction Silver Line), so it does fit the model.

Just wish I had a better place for my mobile rig on the days I go to the office at 75 & Knox - I don't get very good reception from the 3rd level of the underground parking garage.
 

BenScan

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Anybody else heard announcements on 11043 or 11046?
I haven't been paying too close attention to DART lately, but recordings show activity from 11001 up to 11099. My guess is that they are patches based on what I'm seeing.
 
Last edited:

mwjones

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I haven't been paying too close attention to DART lately, but recordings show activity from 11001 up to 11099. My guess is that they are patches based on what I'm seeing.
Good point @BenScan - I had to go back and look at the logs (I only searched for recordings before)...

With a little bit of filtering, I found this...

2025/03/01 13:37:20 Freq=856.812500 NAC=03C Patch/Simulselect Supergroup: TG=11004
2025/03/01 13:37:20 Freq=856.812500 NAC=03C Patch/Simulselect Subgroup: TG=2101 [[Trains 2101] Train Ops (TDMA)]
2025/03/01 13:37:20 Freq=856.812500 NAC=03C Patch/Simulselect Supergroup: TG=11004
2025/03/01 13:37:20 Freq=856.812500 NAC=03C Patch/Simulselect Subgroup: TG=2113 [[Trains 2113] Train Ops (TDMA)]
2025/03/01 13:37:32 Freq=856.812500 NAC=03C Group call; TG=11004 [ (TDMA)] Src=EXTERNAL Ch=857.83750-1 24s

And more recently:

2025/04/11 17:05:04 Freq=860.337500 NAC=04E Patch/Simulselect Supergroup: TG=11020
2025/04/11 17:05:04 Freq=860.337500 NAC=04E Patch/Simulselect Subgroup: TG=2113 [[Trains 2113] Train Ops (TDMA)]
2025/04/11 17:05:04 Freq=860.337500 NAC=04E Patch/Simulselect Supergroup: TG=11020
2025/04/11 17:05:04 Freq=860.337500 NAC=04E Patch/Simulselect Subgroup: TG=2101 [[Trains 2101] Train Ops (TDMA)]
2025/04/11 17:17:59 Freq=860.337500 NAC=04E Patch/Simulselect teardown: TG=11020
2025/04/11 17:27:01 Freq=860.337500 NAC=04E Patch/Simulselect Supergroup: TG=11014
2025/04/11 17:27:01 Freq=860.337500 NAC=04E Patch/Simulselect Subgroup: TG=2113 [[Trains 2113] Train Ops (TDMA)]
2025/04/11 17:27:01 Freq=860.337500 NAC=04E Patch/Simulselect Supergroup: TG=11014
2025/04/11 17:27:01 Freq=860.337500 NAC=04E Patch/Simulselect Subgroup: TG=2101 [[Trains 2101] Train Ops (TDMA)]
2025/04/11 17:54:25 Freq=856.812500 NAC=03C Patch/Simulselect Supergroup: TG=11016
2025/04/11 17:54:25 Freq=856.812500 NAC=03C Patch/Simulselect Subgroup: TG=2113 [[Trains 2113] Train Ops (TDMA)]
2025/04/11 17:54:27 Freq=856.812500 NAC=03C Patch/Simulselect Supergroup: TG=11016
2025/04/11 17:54:27 Freq=856.812500 NAC=03C Patch/Simulselect Subgroup: TG=2101 [[Trains 2101] Train Ops (TDMA)]
So you are correct, it is a patch, in this case between talkgroups 2101 and 2113 - one that is almost constantly nailed up, and gets rebuilt soon after it tears down.
 

mwjones

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Has Dart police officially switched to Encryption ? If so can someone submit it to the database ?
For me it's inconclusive - 4221 and 4222 are encrypted (and 4222 is already marked as such, 4221 has not been submitted), but I don't see any of the other DART PD 42xx talkgroups on the 800MHz sites - I need to switch over and monitor the 700MHz sites with the mobile rig the next time I'm in town.
 

kmartin

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For me it's inconclusive - 4221 and 4222 are encrypted (and 4222 is already marked as such, 4221 has not been submitted), but I don't see any of the other DART PD 42xx talkgroups on the 800MHz sites - I need to switch over and monitor the 700MHz sites with the mobile rig the next time I'm in town.
Thanks. Keep us posted
 
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