Running OP25

n5jrn

Newbie
Joined
Aug 3, 2020
Messages
4
Location
Bellingham, WA
I’ve been attempting to get OP25 to receive my local Customs and Border Patrol frequencies, with limited success. I have found the frequencies just fine (the control frequency on 167.2375 was pretty obvious in gqrx, and it agreed with the RadioReference data for my area). I’m seeing talkgroups become active and inactive (and the TG’s I see make sense for my area), but it only seems like maybe 1 to 5 percent of traffic gets successfully demodulated to audio in my PC’s speaker.

Part of the problem has been an evident lack of documentation about what’s getting displayed in the terminal window. The top line is obviously data pertaining to the control channel. Then come a bunch of lines summarizing what was heard on the various trunking frequencies. The lower left corner displays the frequency currently being monitored, and the lower-right corner the ID of the radio doing the transmission and possibly some other transmission-related information (such as whether or not the traffic is encrypted).

When a frequency is received, first the talk group and frequency are displayed, then as more information becomes available the radio ID and other status information get displayed. A marginal signal might well reault in the frequency and TG getting displayed, but never any further data in the lower-right corner.

Is this understanding basically correct?

If it’s correct, one of the problems that seems to be happening is that eventually OP25 gets “stuck” on a very weak signal that it can’t decode (or even, it appears, successfully recognize when it goes away), and so never comes back to the main control channel but instead becomes permanently silent. The FFT plot shows at best a very weak signal and the constellation plot shows nothing being successfully interpreted into dibits, just a disorganized cloud.

When this happens, hitting the s (skip) key seems to get OP25 unstuck, but apparently at the cost of forever deafening it to the frequency in question (which sometimes has meaningful, strong signals).
 

boatbod

Member
Joined
Mar 3, 2007
Messages
2,692
Location
Talbot Co, MD
Have you pulled the latest update? There was a timer bug that I fixed a day or two ago which might cause hangs on marginal signals.
 

n5jrn

Newbie
Joined
Aug 3, 2020
Messages
4
Location
Bellingham, WA
Those channels are digitally encrypted, if you were expecting to hear un-encrypted audio.
Actually, sometimes I do hear intelligible audio from my computer’s speaker, so not always encrypted. I do realize that the transmissions that cause the “encrypted” message to display are encrypted. I was most interested to confirm if my understanding of what OP25 is doing is basically correct:

When a frequency is received, first the talk group and frequency are displayed, then as more information becomes available the radio ID and other status information get displayed. A marginal signal might well reault in the frequency and TG getting displayed, but never any further data in the lower-right corner.

Is this understanding basically correct?
 

boatbod

Member
Joined
Mar 3, 2007
Messages
2,692
Location
Talbot Co, MD
When a frequency is received, first the talk group and frequency are displayed, then as more information becomes available the radio ID and other status information get displayed. A marginal signal might well reault in the frequency and TG getting displayed, but never any further data in the lower-right corner.

Is this understanding basically correct?
That's basically how it works, particularly with the rx.py variant of trunking. I've changed things around a bit with the multi_rx.py variant, but in a nutshell the UI can only display data when it is available. Many times the Source RID is not passed when op25 first tunes the control channel. Reasons for this might include late-entry, slow tuning, or the network simply not sending it. Mid-call signaling can subsequently provide the RID (or may change it as the conversations flips back and forth) so the internal datastructures get updated and eventually this trickles down to the UI.
 
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