OP25 OP25; I got it running, but a few questions

[moonbounce]

Boatbod

These are the directions I am following Setting up OP25 Scanner Trunking on an Ubuntu Virtual Machine | RadioHobbyist.org and the system I want to listen to is trunked and it is a Motorola Type 2 Smart Zone. I made the changes you suggested and hit enter and all I got was this sign >.

 

[boatbod]

Sorry, op25 does not support smartzone. Try trunkrecorder instead.

 

[W4KRR]

Another question: Should OP25 work with an Airspy? I tried it, but the program doesn't launch.

It stops after "setting gain lna to 47
Using Volk machine: sse4_2_64_orc"

 

[boatbod]

Another question: Should OP25 work with an Airspy? I tried it, but the program doesn't launch.

It stops after "setting gain lna to 47
Using Volk machine: sse4_2_64_orc"

OP25 works with airspy but you'll need different command line parameters.

./rx.py --args "airspy" --gains "LNA:15,MIX:15,IF:8" -S 3000000 ...

Note that you'll have to play with the gains to find the best setting.
The sample width will also be dependent on your hardware. If you pick the wrong one it'll error out at startup.

 

[W4KRR]

This is what I used:
./rx.py --args "airspy" --gains "LNA:6,MIX:6,IF:6" -S 10000000 -f 858.8125e6

I played with the gains numbers, and several different settings seem to work, but I get no audio.

 

[maus92]

How about concatenating -q -2 -T trunk.tsv -V -2 -U 2> stderr.2 to the right of the frequency? If your trunk.tsv (or whatever name you use) file already has a cch frequency in it, you won't need your -f xxx.xxxx parameter. Finally, 10000000 is the max bandwidth of the airspy - it's not necessary to be that large with op25 (use 3000000) since it retunes to the active voice channel, and you will take a performance hit if using low end hardware.

 

[wgbecks]

Note: The minimum sample rate supported is 3000000 for the Airspy Mini, but it's 2500000 for the Airspy R2. These are not interchangeable, so you must apply the correct value to match the specific device.

Also, the LNA, MIX, and IF gain value may be too low unless you're located very close to the tower. Take a look at the constellation plot and adjust the gain value for the most concentration of the symbols (dots) in the four
corners as possible.

I am running the Airspy R2 on an indoor antenna and am located approximately six miles from the 800 MHz system. I find that in my case that my best performance is obtained with maximum gain value settings. IE: ./rx.py --args 'airspy' -S 2500000 -N 'LNA:15,MIX:15,IF:15' But these values are arbitrary as you have to consider available signal levels as well as the presence of other strong nearby inband signals that might cause intermodulation in the SDR if your gain levels are set too high.

Optimum adjustment renders signal to noise ratios better that 20 dB as seen in the FFT plot, and the tight concentration of dots in the four corners representing the symbols as shown in the Constellation plot.

 

[W4KRR]

I got it working with this command line:

./rx.py --args "airspy" --gains "LNA:10,MIX:10,IF:8" -S 2500000 -q -2 -T trunk.tsv -V -2 -U 2> stderr.2

It works, but not until I applied a tuning adjustment of (1500)
Also, the received frequency and talkgroup flicker while receiving a transmission. Didn't happen when using a dongle.

How would I write a script file to launch this, with the (1500) offset applied?

Thanks to all for the help.

 

[boatbod]

I got it working with this command line:

./rx.py --args "airspy" --gains "LNA:10,MIX:10,IF:8" -S 2500000 -q -2 -T trunk.tsv -V -2 -U 2> stderr.2

It works, but not until I applied a tuning adjustment of (1500)
Also, the received frequency and talkgroup flicker while receiving a transmission. Didn't happen when using a dongle.

How would I write a script file to launch this, with the (1500) offset applied?

Thanks to all for the help.

1500 fine tune is excessive; I recommend you adjust your ppm offset "-q -2" in the script above. Once you get the fine tune lower than +/-400 you can set it at startup with the "-d" parameter.

 

[maus92]

It strikes me that -q -2 is an extraordinary large correction for an Airspy. Perhaps eliminating that altogether, and use -d 500 ? IDK, I hope to experiment with my R2 later today.

 

[W4KRR]

It strikes me that -q -2 is an extraordinary large correction for an Airspy. Perhaps eliminating that altogether, and use -d 500 ? IDK, I hope to experiment with my R2 later today.

After some experimenting, I changed the -q value to zero, and now it seems to be working well. I have not yet experimented with the -d parameter, maybe I'll fool around with that later.

 

[maus92]

I got my Airspy running; 10 for the gains all around, -q 0, -d 50. Mixer graph values vary between 0 and 4 or 5, which is better than I can get with a Nooelec TCXO. I am less than a mile from a simulcast site in the 700 band.

 

[foxtail]

PPM can be used as -q -2.5, 87.5, etc.... Sometimes one dongle I ajd. to is -q -3.5. Another older one -q 88.5