P25 TDMA Control Channel decoding -- requesting help from experts

[AuggieActually]

Is this a possible p2 tdma cc? The latest version of DSDplus insists on decoding this channel as p25p2, but I'm only getting "Data Not Available" and "Bad DUID" messages.

For the record, this frequency is most likely MARCS, the Ohio state-wide system, the next closest assignment on this frequency that I can find is more than half a state away. I'm in southwest Ohio, and can decode both MARCS and the new Duke p2 with no issues with this same setup.

Frequency: 856.0875Mhz

Things to note:
The audio "sound" is most similar to the new duke p25 cc, with some similarity to the marcs cc that I can here. It definitely sounds more like p25 than any of the other digital control channels.

The zip file compressed by a huge factor, which indicates lots of repeating, identical data, so likely not a random data transmission, and definitely not random noise.

I tuned this signal with 2 different sdr's, fmpa and fmp24, and with a BCD436HP. All sound the same, so likely not some weird interference/phantom channel.

Only other explanation I can think of is that it's a wireless backhaul/data stream for MARCS.

 

[btt]

Is this a possible p2 tdma cc? The latest version of DSDplus insists on decoding this channel as p25p2, but I'm only getting "Data Not Available" and "Bad DUID" messages.

It doesn't appear to be P2 TDMA CC. Zero P2 syncs detected. Looks like a different symbol rate at first glance.

 

[AuggieActually]

It doesn't appear to be P2 TDMA CC. Zero P2 syncs detected. Looks like a different symbol rate at first glance.

Well, that answers that question. I wonder why DSDPlus is insisting on trying to decode it like one, then. Any clue where I should go to find out what it might be?

 

[btt]

Well, that answers that question. I wonder why DSDPlus is insisting on trying to decode it like one, then. Any clue where I should go to find out what it might be?

It is 4-fsk, but it is at a rate of 1200 sym/sec vs 6000 sym/sec that P2 uses and 4800 sym/sec for P1.

 

[scannerboy02]

Is this a possible p2 tdma cc? The latest version of DSDplus insists on decoding this channel as p25p2, but I'm only getting "Data Not Available" and "Bad DUID" messages.

For the record, this frequency is most likely MARCS, the Ohio state-wide system, the next closest assignment on this frequency that I can find is more than half a state away. I'm in southwest Ohio, and can decode both MARCS and the new Duke p2 with no issues with this same setup.

Frequency: 856.0875Mhz

Things to note:
The audio "sound" is most similar to the new duke p25 cc, with some similarity to the marcs cc that I can here. It definitely sounds more like p25 than any of the other digital control channels.

The zip file compressed by a huge factor, which indicates lots of repeating, identical data, so likely not a random data transmission, and definitely not random noise.

I tuned this signal with 2 different sdr's, fmpa and fmp24, and with a BCD436HP. All sound the same, so likely not some weird interference/phantom channel.

Only other explanation I can think of is that it's a wireless backhaul/data stream for MARCS.

The FCC website is running EXTREMELY slow today so not being able to look up the frequency at this moment, I believe this frequency is part of the MARCS data network for in car computers.

 

[ralexander5]

Had both the BTT p25rx and DSDplus running on same 1F8 AEP site and captured some traffic. Noticed that there is difference in the way the Radio ID is shown in the DSD event log. The 1R-log and P25rx logs show the same id. Have not been able to get any audio from DSD. It captures other P25 systems but not the TDMA CC ones.

There was a earlier question on the voice channel used. The second slot on the CC frequency is the primary one use. Does not rotate.

1R-DSDplus-event
2021/08/07 19:37:56 Freq=854.762500 NAC=02C Group call; TG=6229 RID=9806205 Ch=854.7625-2 2s
2021/08/07 19:38:03 Freq=854.762500 NAC=02C Group call; TG=6229 Src=EXTERNAL Ch=854.7625-2 1s
2021/08/07 19:38:06 Freq=854.762500 NAC=02C Group call; TG=6229 RID=9806205 Ch=854.7625-2 2s
2021/08/07 19:38:09 Freq=854.762500 NAC=02C Group call; TG=6229 Src=EXTERNAL Ch=854.7625-2 4s
2021/08/07 19:38:18 Freq=854.762500 NAC=02C Group call; TG=6229 RID=9806205 Ch=854.7625-2 3s
2021/08/07 19:38:23 Freq=854.762500 NAC=02C Group call; TG=6229 Src=EXTERNAL Ch=854.7625-2 2s


BTT p25rx_recmeta
P25P2 854.762500 MHz, TG 6229 , AEP GW,2021-08-07-19:37:56,-105 dbm,58880, cc_freq 854.762500 mhz,RID 6001655,AEP,,P2
P25P2 854.762500 MHz, TG 6229 , AEP GW,2021-08-07-19:38:04,-107 dbm,61613, cc_freq 854.762500 mhz,RID 6001653,AEP,,P2
P25P2 854.762500 MHz, TG 6229 , AEP GW,2021-08-07-19:38:07,-107 dbm,63934, cc_freq 854.762500 mhz,RID 6001655,AEP,,P2
P25P2 854.762500 MHz, TG 6229 , AEP GW,2021-08-07-19:38:10,-108 dbm,66486, cc_freq 854.762500 mhz,RID 6001653,AEP,,P2
P25P2 854.762500 MHz, TG 6229 , AEP GW,2021-08-07-19:38:18,-104 dbm,74689, cc_freq 854.762500 mhz,RID 6001655,AEP,,P2
P25P2 854.762500 MHz, TG 6229 , AEP GW,2021-08-07-19:38:23,-105 dbm,79481, cc_freq 854.762500 mhz,RID 6001653,AEP,,P2
DSDplus 1R-log
2021.08.07 19:37:55 MAC_IDLE Null Information
2021.08.07 19:37:56 LCCH DCC=02C PDU=1C81A40C09110D830A83F2853608068888888802C
2021.08.07 19:37:56 MAC_IDLE Null Information
2021.08.07 19:37:56 LCCH DCC=02C PDU=1C8FA4070A26000A080B88888888888888888802C
2021.08.07 19:37:56 MAC_IDLE Null Information
2021.08.07 19:37:56 LCCH DCC=02C GRP_V_CH_GRANT PRI4 TG=6229 RID=9806205 ch=854.7625-2
2021.08.07 19:37:56 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001655
2021.08.07 19:37:56 LCCH DCC=02C RFSS_STS_BCST SysID=1F8 LRA=4 RFSS=44 Site=44 CC=854.7625-1 SC=70
2021.08.07 19:37:56 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:37:56 MAC_ACTIVE Null Information
2021.08.07 19:37:56 LCCH DCC=02C NET_STS_BCST WACN ID=92715 SysID=1F8 LRA=4 CC=854.7625-1 SC=70
2021.08.07 19:37:56 LCCH DCC=02C SCCB RFSS=44 Site=44 [ch=858.3625-1 SSC=04] [ch=855.8625-1 SSC=04]
2021.08.07 19:37:56 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001655
2021.08.07 19:37:56 LCCH DCC=02C SYNC_BCST US=0 IST=0 MMU=0 MC=0 VL=0 LTO=0 2021/08/08 00:00 uSlot=3368
2021.08.07 19:37:56 Bad Frame Data
2021.08.07 19:37:56 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:56 Bad Frame Data
2021.08.07 19:37:56 LCCH DCC=02C SN-DATA_CHN_ANN_EXP DSO=00 TXch=851. RXch=851. DAC=FFFF
2021.08.07 19:37:56 (F7S2-4V)
2021.08.07 19:37:56 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:56 (F9S2-4V)
2021.08.07 19:37:56 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:37:56 LCCH DCC=02C PDU=1C81A40C09110D830A83F2853608068888888802C
2021.08.07 19:37:56 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:56 (F1S2-4V)
2021.08.07 19:37:56 LCCH DCC=02C PDU=1C8FA4070A26000A080B88888888888888888802C
2021.08.07 19:37:56 (F3S2-4V)
2021.08.07 19:37:56 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:56 (F5S2-2V)
2021.08.07 19:37:56 LCCH DCC=02C RFSS_STS_BCST SysID=1F8 LRA=4 RFSS=44 Site=44 CC=854.7625-1 SC=70
2021.08.07 19:37:56 (F7S2-4V)
2021.08.07 19:37:56 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:56 (F9S2-4V)
2021.08.07 19:37:56 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001655
2021.08.07 19:37:56 LCCH DCC=02C NET_STS_BCST WACN ID=92715 SysID=1F8 LRA=4 CC=854.7625-1 SC=70
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F1S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C IDEN_UP ID=0 Base=851. Offset=-45 Spacing=12.5 BW=12.5
2021.08.07 19:37:57 (F3S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F5S2-2V)
2021.08.07 19:37:57 LCCH DCC=02C SYS_SRV_BCST SSA=0F2C36 SSS=0F2C36 RPL=1
2021.08.07 19:37:57 (F7S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F9S2-4V)
2021.08.07 19:37:57 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:37:57 LCCH DCC=02C ADJ_STS_BCST SysID=1F8 LRA=4 RFSS=8 Site=8 CC=859.7875-1 SC=70 CFVA=3: Networked
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F1S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C PDU=1C81A40C09110D830A83F2853608068888888802C
2021.08.07 19:37:57 (F3S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F5S2-2V)
2021.08.07 19:37:57 LCCH DCC=02C PDU=1C8FA4070A26000A080B88888888888888888802C
2021.08.07 19:37:57 (F7S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F9S2-4V)
2021.08.07 19:37:57 MAC_ACTIVE Null Information
2021.08.07 19:37:57 LCCH DCC=02C RFSS_STS_BCST SysID=1F8 LRA=4 RFSS=44 Site=44 CC=854.7625-1 SC=70
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F1S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C NET_STS_BCST WACN ID=92715 SysID=1F8 LRA=4 CC=854.7625-1 SC=70
2021.08.07 19:37:57 (F3S2-4V)
2021.08.07 19:37:57 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:37:57 (F5S2-2V)
2021.08.07 19:37:57 LCCH DCC=02C SCCB RFSS=44 Site=44 [ch=857.3125-1 SSC=04] [ch=858.3625-1 SSC=04]
2021.08.07 19:37:57 (F7S2-4V)
.
.
021.08.07 19:38:03 LCCH DCC=02C IDEN_UP_TDMA ID=8 Base=851. Offset=-45 Spacing=12.5 BW=12.5 Slots=2
2021.08.07 19:38:03 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001653
2021.08.07 19:38:03 LCCH DCC=02C SYS_SRV_BCST SSA=0F2C36 SSS=0F2C36 RPL=1
2021.08.07 19:38:03 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:38:03 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001653
2021.08.07 19:38:03 LCCH DCC=02C ADJ_STS_BCST SysID=1F8 LRA=4 RFSS=57 Site=57 CC=855.0625-1 SC=70 CFVA=3: Networked
2021.08.07 19:38:03 LCCH DCC=02C PDU=1C81A40C09110D830A83F2853608068888888802C
2021.08.07 19:38:03 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:38:03 LCCH DCC=02C PDU=1C8FA4070A26000A080B88888888888888888802C
2021.08.07 19:38:03 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001653
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:38:04 LCCH DCC=02C RFSS_STS_BCST SysID=1F8 LRA=4 RFSS=44 Site=44 CC=854.7625-1 SC=70
2021.08.07 19:38:04 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001653
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:38:04 MAC_ACTIVE Group Voice Channel User Slot#2 PRI4 TG=6229 RID=6001653
2021.08.07 19:38:04 LCCH DCC=02C NET_STS_BCST WACN ID=92715 SysID=1F8 LRA=4 CC=854.7625-1 SC=70
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 Bad Frame Data
2021.08.07 19:38:04 LCCH DCC=02C SCCB RFSS=44 Site=44 [ch=855.8625-1 SSC=04] [ch=857.3125-1 SSC=04]
2021.08.07 19:38:04 Bad Frame Data
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 (F5S2-4V)
2021.08.07 19:38:04 LCCH DCC=02C SYNC_BCST US=0 IST=0 MMU=0 MC=0 VL=0 LTO=0 2021/08/08 00:00 uSlot=4440
2021.08.07 19:38:04 (F7S2-4V)
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 (F9S2-4V)
2021.08.07 19:38:04 MAC_ACTIVE Unhandled MFIDA4 OSP
2021.08.07 19:38:04 LCCH DCC=02C SN-DATA_CHN_ANN_EXP DSO=00 TXch=851. RXch=851. DAC=FFFF
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 (F1S2-4V)
2021.08.07 19:38:04 LCCH DCC=02C PDU=1C81A40C09110D830A83F2853608068888888802C
2021.08.07 19:38:04 (F3S2-2V)
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 (F5S2-4V)
2021.08.07 19:38:04 LCCH DCC=02C PDU=1C8FA4070A26000A080B88888888888888888802C
2021.08.07 19:38:04 (F7S2-4V)
2021.08.07 19:38:04 LCCH DCC=02C GRP_V_CH_GRANT_UPDT TG=6229 ch=854.7625-2
2021.08.07 19:38:04 (F9S2-4V)
2021.08.07 19:38:04 MAC_ACTIVE Null Information
2021.08.07 19:38:04 LCCH DCC=02C RFSS_STS_BCST SysID=1F8 LRA=4 RFSS=44 Site=44 CC=854.7625-1 SC=70