Control channel not connecting / remaining idle

[Matt Swift]

Hello fellow SDRers,

I've been trying to setup SDRTrunk to work with the Seattle / King County public safety system (https://www.radioreference.com/apps/db/?sid=604). I was able to get a successful setup with Unitrunker so know that I have the right frequencies, and that my setup in general works. 

I seem to have a good control signal (see images below), and have played about with the tuner gain and PPM to no avail. The Control channel refuses to lock on, and remains as IDLE status with a stream of messages similar to:

2021:08:14 13:25:17    APCO-25    0    <-> SYNC LOSS - BITS PROCESSED [9600]
2021:08:14 13:25:16    APCO-25    0    <-> SYNC LOSS - BITS PROCESSED [1570]

My exact same setup in Unitrunker seems to work just fine, and picks up a very healthy signal. I'm not quite sure what I may be doing wrong, but would appreciate any input you may have.

[Matt Swift]

Higher resolution pictures shown below.

[GTR8000]

SDRTrunk does not decode Motorola SmartZone (aka Type II or 3600) control channels, and thus can't trunk track any SmartZone system.

The software is capable of decoding individual SmartZone traffic channels, but only when they use the P25 CAI. The 3D1C system is 99% analog, so you're out of luck.

Unitrunker would be the preferred software for SmartZone decoding, which you're already using, so stick with that.

[Matt Swift]

Thanks for the quick feedback!

[rlm...@gmail.com]

A new P25 Phase 2 system is in testing now, scheduled to roll-out this fall. So, hang onto your SDRTrunk............

https://psern.org

[Jeff Thompson]

Hopefully that new P2 system won't have P2/TDMA control channels, or maybe Denny will come back to add P2 control channels.

[rlm...@gmail.com]

The latest boatbod version of OP25 will do TDMA control channels

[Ulti P. Uzzer]

The current version of SDRTrunk (that has been out since last yr), does P25 Phase II perfectly.

[brett.f...@gmail.com]

On Wednesday, August 18, 2021 at 12:45:57 PM UTC-5 bwbra...@gmail.com wrote:

The current version of SDRTrunk (that has been out since last yr), does P25 Phase II perfectly.

They are talking specifically about TDMA control channels which is a relatively new development that has been recently discovered in the wild. Up until now all P25 trunking systems, whether Phase I or Phase II voice, have used the same FDMA control channel configuration, just with additional/different messages for Phase II systems.

These new systems that have been discovered are using an actual TDMA control channel, one slot is used for control data and the second as a Phase II voice channel. These control channels are not capable of being decoded by existing Phase II receivers without updates to be able to handle the new control channel format, which currently includes SDRTrunk.

To my knowledge this control channel type is currently only used by Harris, and has been discovered on a very small number of new commercial trunking systems. Not in use by any public safety systems, yet. Both the Osmocom and boatbod versions of OP25 have been updated with the capability of tracking these systems.