OP25 - RaspberryPI tsbks Stops Increasing

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spydervw

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I think have have OP25 configured correctly for the local P25 system in my area but have a problem.

Here is where I am...
Was able to find the control channel and get the NAC. Running rx.py in non-trunk mode shows the right frequency and the tsbks keep increasing during the session.
I edited trunk.tsv for the local system and run rx.py with the trucking parameters in the command. The window comes up and the tsbks increases until it hits the first voice frequency pops up and then stops. The frequency that was originally there is now zeros. If I open Gnuplot, the tuned frequency is not on the control frequency any more and is almost like it will not tune back to the control channel. Any ideas?

89050
 

boatbod

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Are you sure that is the control channel rather than a voice channel? SYSID, WACN and CC Freq are all 0 which implies you're not actually listening to the right freq.

What's your rx.py command line and what (RRDB) system are you trying to listen to?
Do you see anything in the stderr.2 log file?
 
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spydervw

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Mar 29, 2005
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The SYSID, WACN and CC Freq are all populated with values but when it switches to first talkgroup it changes to all zeros.

Here is the system that I am trying to monitor...

Control channel shows 851.225 on RR but it is closer to 851.615 on my RTLv3 dongle so I am using an offset of 390000.

This is my command line...
./rx.py --args 'rtl' -N 'LNA:40' -S 2500000 -T trunk.tsv -q 2 -V -2 -n -U 2>stderr-stream0.2

Trunk file...
89058

stderr.2
Code:
gr-osmosdr 0.1.5 (0.1.5) gnuradio 3.7.14.0
built-in source types: file fcd rtl rtl_tcp hackrf rfspace airspy soapy redpitaya
Using device #0 Realtek RTL2838UHIDIR SN: 00000001
Found Rafael Micro R820T tuner
[R82XX] PLL not locked!
gain: name: LNA range: start 0 stop 0 step 0
setting gain LNA to 40
supported sample rates 250000-2560000 step 24000
Exact sample rate is: 2500000.107620 Hz
[R82XX] PLL not locked!
Using two-stage decimator for speed=2500000, decim=25/4 if1=100000 if2=25000
Project 25 IMBE Encoder/Decoder Fixed-Point implementation
Developed by Pavel Yazev E-mail: X
Version 1.0 (c) Copyright 2009
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; see the file ``LICENSE'' for details.
op25_audio::open_socket(): enabled udp host(127.0.0.1), wireshark(23456), audio(23456)
p25_frame_assembler_impl: do_imbe[1], do_output[0], do_audio_output[1], do_phase2_tdma[1], do_nocrypt[1]
metadata update not enabled
using ALSA sound system
audio device: default
Listening on 127.0.0.1:23456
Allocating 15 zero-copy buffers
Flowgraph completed. Exiting

Thanks in advance for your help!
 

boatbod

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That's a rediculously large offset that is undoubtedly masking another issue. Unless you have a DC spike in your dongle I recommend setting it to 0. You can also change your sample rate to something lower (e.g. -S 1000000) as there is no need to stretch the limits of the sdr hardware.
Is the (-q 2) ppm correction of 2 verified from your usage with DSDFL?

Suggest making the changes above and then turning on the fft plot (#1) and seeing if the tuning line is centered on a signal peak.
Anything in the log?
 

spydervw

Newbie
Joined
Mar 29, 2005
Messages
3
That's a rediculously large offset that is undoubtedly masking another issue. Unless you have a DC spike in your dongle I recommend setting it to 0. You can also change your sample rate to something lower (e.g. -S 1000000) as there is no need to stretch the limits of the sdr hardware.
Is the (-q 2) ppm correction of 2 verified from your usage with DSDFL?

Suggest making the changes above and then turning on the fft plot (#1) and seeing if the tuning line is centered on a signal peak.
Anything in the log?
I changed the sample rate to 1000000, zeroed out the offset, needed to bump the -q value to -455 center the peak in the plot. It still stops decoding after the first trunkgroup is hit. If I remove the -t and add the -f 851.2250e6 argument, it is very stable and the tsbks keep increasing until I close the app.


Here is the logfile with verbosity turned up...
Code:
gr-osmosdr 0.1.5 (0.1.5) gnuradio 3.7.14.0
built-in source types: file fcd rtl rtl_tcp hackrf rfspace airspy soapy redpitaya
Using device #0 Realtek RTL2838UHIDIR SN: 00000001
Found Rafael Micro R820T tuner
[R82XX] PLL not locked!
gain: name: LNA range: start 0 stop 0 step 0
setting gain LNA to 10
supported sample rates 250000-2560000 step 24000
Exact sample rate is: 1000000.026491 Hz
[R82XX] PLL not locked!
Using two-stage decimator for speed=1000000, decim=10/4 if1=100000 if2=25000
Project 25 IMBE Encoder/Decoder Fixed-Point implementation
Developed by Pavel Yazev E-mail: x
Version 1.0 (c) Copyright 2009
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; see the file ``LICENSE'' for details.
op25_audio::open_socket(): enabled udp host(127.0.0.1), wireshark(23456), audio(23456)
p25_frame_assembler_impl: do_imbe[1], do_output[0], do_audio_output[1], do_phase2_tdma[0], do_nocrypt[1]
07/30/20 10:18:18.661919 set control channel=851.225000
metadata update not enabled
using ALSA sound system
audio device: default
Listening on 127.0.0.1:23456
Allocating 15 zero-copy buffers
Allocating 15 zero-copy buffers
07/30/20 10:18:20.750937 control channel timeout
07/30/20 10:18:20.751675 do_metadata state=1: [None] None
07/30/20 10:18:20.915198 add_patch: tgid(1868) is patched to sg(65123)
07/30/20 10:18:21.087153 add_patch: tgid(10703) is patched to sg(65398)
07/30/20 10:18:21.103383 set tgid=52104, srcaddr=0
07/30/20 10:18:21.104361 new tgid=52104 JC Event 9 prio 3
07/30/20 10:18:21.105965 new freq=851.825000
07/30/20 10:18:21.106542 set tgid=57027, srcaddr=0
07/30/20 10:18:21.106802 new tgid=57027 Detention F1 prio 3
07/30/20 10:18:21.107380 new freq=858.762500
07/30/20 10:18:21.107755 voice update:  tg(52104), freq(851825000), slot(-), prio(3)
07/30/20 10:18:21.107982 do_metadata state=0: [52104] JC Event 9
07/30/20 10:18:21.212679 add_patch: tgid(50066) is patched to sg(65398)
07/30/20 10:18:21.222611 set tgid=52104, srcaddr=0
07/30/20 10:18:21.222960 set tgid=57027, srcaddr=0
07/30/20 10:18:21.226768 add_patch: tgid(1805) is patched to sg(65117)
07/30/20 10:18:21.275666 set tgid=52104, srcaddr=0
07/30/20 10:18:21.276271 set tgid=57027, srcaddr=0
07/30/20 10:18:21.315954 add_patch: tgid(7722) is patched to sg(65117)
07/30/20 10:18:21.401025 set tgid=57022, srcaddr=5701212
07/30/20 10:18:21.401341 new tgid=57022 Talkgroup ID 57022 [0xdebe] prio 3
07/30/20 10:18:21.403062 new freq=853.062500
07/30/20 10:18:21.411099 set tgid=57022, srcaddr=5701212
07/30/20 10:18:21.528144 set tgid=52104, srcaddr=0
07/30/20 10:18:21.528585 set tgid=57027, srcaddr=0
Flowgraph completed. Exiting
 

boatbod

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Joined
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Messages
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Location
Talbot Co, MD
I changed the sample rate to 1000000, zeroed out the offset, needed to bump the -q value to -455 center the peak in the plot. It still stops decoding after the first trunkgroup is hit. If I remove the -t and add the -f 851.2250e6 argument, it is very stable and the tsbks keep increasing until I close the app.
-455ppm error correction? No way! Even the crappy old non-txco dongles were never that far off.
You're dialing in a 390khz frequency correction which is crazy and certainly guaranteed to make sure you never tune anything other than whatever you picked up at startup.

I suggest you set -q 0 and then look at the fft plot like I suggested earlier today. I'm going to bet your signal peak is located at 851.6125Mhz and that the control channel is there, not 851.225Mhz.
 
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