DSD+ "Decode Inbound P25 CC" doesn't work?

[kv6o]

I am trying to use DSD+ to monitor and decode the Inbound Service Packets on the uplink frequency of a P25 Phase 1 system. Oddly, when I enable the option, "Decode Inbound P25 CC" - it doesn't work... no decodes. If I disable that feature... it works. Not sure what the feature/function is supposed to do? I am monitoring the uplink frequency in both cases. I am able to test, I have a subscriber radio right here with me... and I am the system manager of the system so I can send thing's like "Status Check" and it shows up as "Radio Check ACK Tgt=XXXXXX Src FNE" This is what I am after... pinging a radio and seeing a received response in DSD+.

I was hoping to be able to do this on a Raspberry Pi with OP25, but that doesn't seem to be possible.

Goal here is to be able to use a remote receiver and listen for a response to a status check command. This seems to be working, just thought I'd check on this "Decode Inbound P25 CC" functionality.

Thanks for any input/advice!

Steve

 

[BM82557]

Fyi --

P25 uplink decoding (inbound signal packets)

I am looking for software that can decode and display the Inbound Signal Packets for a P25 Phase I (FDMA) system. I am playing with Unitracker, but it appears to log the inbound packets only - I have to stop the decoder and open the log to see what it decoded. Anyone know of anything...

forums.radioreference.com

 

[kv6o]

I was part of that thread too... DSD+ is working how I'd like, I am just curious what that setting is for, because it sure doesn't seem to do what it says it does.

 

[mtindor]

I am trying to use DSD+ to monitor and decode the Inbound Service Packets on the uplink frequency of a P25 Phase 1 system. Oddly, when I enable the option, "Decode Inbound P25 CC" - it doesn't work... no decodes. If I disable that feature... it works. Not sure what the feature/function is supposed to do? I am monitoring the uplink frequency in both cases. I am able to test, I have a subscriber radio right here with me... and I am the system manager of the system so I can send thing's like "Status Check" and it shows up as "Radio Check ACK Tgt=XXXXXX Src FNE" This is what I am after... pinging a radio and seeing a received response in DSD+.

I was hoping to be able to do this on a Raspberry Pi with OP25, but that doesn't seem to be possible.

Goal here is to be able to use a remote receiver and listen for a response to a status check command. This seems to be working, just thought I'd check on this "Decode Inbound P25 CC" functionality.

Thanks for any input/advice!

Steve

DSDPlus is a windows app, thus no RPI support.


Added menu options to tune to trunked repeater inputs when following voice or data calls.
Performance on input frequencies may be improved by selecting only a single protocol
in the DSD+ Decoder menu. For non-P25, non-DFA systems, input frequencies will need to be
added to the relevant DSDPlus.frequencies file entries.

Added proper decoding of inbound P25 trunking control channel messages (ISPs).
When monitoring inbound P25 control channels, only P25 decoding should be selected
in the DSD+ Decoder menu. All other protocols must be deselected.
Currently, only a limited set of ISPs are fully decoded. Decoding of additional ISPs
will be added as users submit raw source audio recordings of unhandled ISPs.
File sizes can be minimized by enabling Only Record During Sync in the DSD+ Input menu.

 

[joescanner]

Only thing I can add is that if you have a multicast system, are you sure that your subscriber is on the same site that you're monitoring the CC freq on? I recently used the DSD+ ISP function and it worked swimmingly (even surprising me by showing me mobile affs/regs ~12 miles away from my location).

 

[boatbod]

I was hoping to be able to do this on a Raspberry Pi with OP25, but that doesn't seem to be possible.

P25 Trunking ISPs have a different message structure than OSPs, and the Subscriber->RFSS uplink will be transmitted with different modulation than the downlink in most certain circumstances. For these reasons, and also fundamentally because receiving ISPs requires you to be physically close to the subscriber, op25 boatbod has never implemented the ability to receive and decode ISPs. I think Max (osmocom) experimented with trying to receive the TDMA uplink but I don't think he got it to work reliably.