Setting Up Unitrunker For Montgomery County Ohio MARCS

[Fletch]

I hope this is the correct forum for this question. I monitored Montgomery County TRS with Unitrunker successfully for years. When they recently moved to the Ohio MARCS system I entered the control channel 853.600 into my Bearcat BCT8 and created a new system in Unitrunker (SID 6643). I then imported that system from Radio Reference and I get no frequency information or activity. I planed on using the BCT8 for data channel monitoring and A BCD536HP for voice. The Unitrunker oscilloscope application seems to be receiving the data channel correctly. The BCT8 is using a discriminator tap into the audio input of the PC. Like I said this worked fine for years. Radio Reference shows Montgomery County using only 800Mhz channels for data. I've never monitored a multi-site system before and apparently don't understand how to set this up in Unitrunker. Any help would be appreciated.

Thanks

 

[SCPD]

Clearly you're monitoring a P25 system.

Ohio MARCS-IP: Multi-Agency Radio Communications (P25) Trunking System, Various, Ohio - Scanner Frequencies

A Motorola system can be decoded even if the audio is slightly clipped. Not so for P25.

Audio Recording Level Adjustment

If you post an image of the scope trace, we can offer suggestions.

 

[Fletch]

Thank you for the reply. Attached is what I'm seeing with UniScope.exe. I'm using an 800Mhz mobile antenna on a window sill.

 

[SCPD]

That's not bad. Increase the gain on the host PC recording device just enough that it fills the 'scope window without clipping - around 80%.

On your signal role receiver tied to the BCT8, set the sample rate to 96000. The challenge here is that this is a CQPSK waveform that you're trying to decode from a ~15 khz wide FM demodulator. The IF filter is a few khz too wide.

If the signal is relatively strong, you'll get decent results.

Consider throwing a cheap SDR into the mix. They are relatively deaf compared to some scanners but they have the advantage of custom tailoring the IF bandwidth to fit.

 

[Fletch]

Thanks for the suggestion. The UniScope pattern looks like this after increasing the audio. Still no data display. When you say SDR are you suggesting using a Software Defined Radio software? If so I'm not familiar how this works, but I'm keen to try.

 

[SCPD]

That looks like a healthy CQPSK waveform. You should be getting good results.

Please post an image of the VCO tab for the signal role receiver. You may need to stretch the window vertically so that all settings are visible at once.

 

[Fletch]

Here it is. Thanks for the reply

 

[Fletch]

Issue Resolved

I found the issue. My receiver settings were incorrect. It was set as a control radio, rather than a signal radio. Once I made the change and selected the audio source the signal came streaming in. Thank you so much for replying to my post, I apologize for being stupid, I should have caught this one myself.