Sample IQ File for P25p2?

[mtindor]

I’ve got a better idea. Why don’t you just record some raw audio coming from a voice channel at a time when the control channel shows TDMA activity in the event log window. Then upload that raw audio to some free site where others can then go download it and experiment with it. Or send it to my Gmail address and I’ll put it where I and others can access it. But you’ve got to be running in combine CC/VC monitoring mode and have to record the role audio when you know there’s supposed to be TDMA traffic occurring.

And if you are willing to do that, maybe you will provide a screenshot of every menu, input, output, control, window, miscellaneous everything so that we can see what options you have sit and don’t have set

 

[NickFi]

I just thought

I’ve got a better idea. Why don’t you just record some raw audio coming from a voice channel at a time when the control channel shows TDMA activity in the event log window. Then upload that raw audio to some free site where others can then go download it and experiment with it. Or send it to my Gmail address and I’ll put it where I and others can access it. But you’ve got to be running in combine CC/VC monitoring mode and have to record the role audio when you know there’s supposed to be TDMA traffic occurring.

Hi Mike. In my case, there is a lot of traffic and all of it is P25p2 and now I can demodulate all calls just fine. I will record a raw audio file in some location and provide the link to it.

 

[NickFi]

I uploaded a raw WAV file here: Easyupload.io - Upload Files and Share Them Easily
Please let me know if it's good.

 

[NickFi]

And if you are willing to do that, maybe you will provide a screenshot of every menu, input, output, control, window, miscellaneous everything so that we can see what options you have sit and don’t have set

Just to be clear - I can do that, but what would be the purpose? With your help, I already solved the demodulation of P25p2.

 

[mtindor]

Just to be clear - I can do that, but what would be the purpose? With your help, I already solved the demodulation of P25p2.

Oh, I didn't realize that. Well then, no point in it

 

[mtindor]

Just to be clear - I can do that, but what would be the purpose? With your help, I already solved the demodulation of P25p2.

What ended up being the issue? And I'm glad you got it fixed!

 

[NickFi]

What ended up being the issue? And I'm glad you got it fixed!

The issue was my lack of knowledge. I was not aware about having to select a control channel frequency. I didn't know that we can automatically receive calls from multiple parties without having to change the frequency. I also didn't know that when I see "TDMA" in the log, this is indicative of a P25p2 transmission. I was expecting that I should see a line with "P25p2", the same as I see for "P25p1" and that is not the case. I read very little about APCO transmissions and I only got to the part where they say that P25p2 occupies half of the channel bandwidth of P25p1. But I didn't read further, to realize they achieve this by TDMA and not by really halving the channel bandwidth. I hope I don't make a fool of myself, since I still haven't read enough about how these things work

And thank you very much for helping me in this aspect, much appreciated!

 

[mtindor]

The issue was my lack of knowledge. I was not aware about having to select a control channel frequency. I didn't know that we can automatically receive calls from multiple parties without having to change the frequency. I also didn't know that when I see "TDMA" in the log, this is indicative of a P25p2 transmission. I was expecting that I should see a line with "P25p2", the same as I see for "P25p1" and that is not the case. I read very little about APCO transmissions and I only got to the part where they say that P25p2 occupies half of the channel bandwidth of P25p1. But I didn't read further, to realize they achieve this by TDMA and not by really halving the channel bandwidth. I hope I don't make a fool of myself, since I still haven't read enough about how these things work

And thank you very much for helping me in this aspect, much appreciated!

If I was of any help at all, I'm glad to have been of help Enjoy! I did try that audio file you put up, and the output sounds great.

 

[NickFi]

If I was of any help at all, I'm glad to have been of help Enjoy! I did try that audio file you put up, and the output sounds great.

You were of great help! Others also contributed with advice, but I did not understand it until you "translated" it for me And you also indicated a link where I can find other services in Australia, which I was also not aware of. The sound is great because of the good system used. Also, my two trees significantly contributed by supporting my antenna

 

[mtindor]

You were of great help! Others also contributed with advice, but I did not understand it until you "translated" it for me And you also indicated a link where I can find other services in Australia, which I was also not aware of. The sound is great because of the good system used. Also, my two trees significantly contributed by supporting my antenna

I've historically stuck with proper vertical or yagi antennas for monitoring VHF/UHF stuff. However, I over the years I've found it convenient many times to switch to a wire I have up for HF. It's a horizontal wire that is clearly not meant for use on VHF/UHF. But it comes in handy, especially because it can decrease some types of noise. Signal strength is never as heigh as it might be if I were using the proper VHF/UHF antenna, but I also monitor from a city location with a ton of strong signals from a local 700/800 mhz simulcast cell and multiple strong DMR systems with transmitters just a mile away. Using the wire helps in that the big signals are attenuated pretty good and the smaller signals still have a pretty good SNF (signal-to-noise ratio). I've always been surprised how much I could hear on a simple wire that is meant for HF. Of course, this setup is not useful if you are trying to DX VHF/UHF signals that are 20+ miles away. But it's a nice tool in the arsenal.

 

[TSW52]

I'm also looking for a P2 IQ file,There's no signal near me,I need to debug DSD Code,Can you send me a file?

 

[boatbod]

The challenge with decoding P25P2 audio is that you have to know the several pieces of information from the control channel before you can decode a voice channel, unlike P25P1 where you can just tune in and start listening. If you therefore want to replay a captured call from an .IQ file, your software has to "think" is is listening first to the control channel, then "tuning" to a voice channel so that it can set the appropriate descramble xor mask. If you don't set the xor mask, you're just going to be decoding gibberish.

 

[dandadj]

That is really useful information about needing information from the control channel in order to decode a P25P2 voice channel. I've recently started using @boatbod 's fork of OP25 with success listening to a local trunked P25P2 system. I find myself now in a similar situation, trying to turn recordings of IQ samples later into audio files to listen to. I'm able to listen to the live system using my RTL-SDR and multi_rx.py, but I've now been trying to get it to work off of a recorded IQ file, like a SIGMF file, using this example config. I have example recordings of just the voice channel when it is active, and wider spectrum recordings that include the control channel and the voice channel. I've had no success so far getting any audio out, or better yet, and audio recording. Given what you've said now about needing to know info from the control channel, I'm wondering if there is a way to use the IQ recording that includes the control channel and the voice channel, or some other way to accomplish this task. So far OP25 is the best tool I've found for the job, but I'm wondering if this use case is too niche or likely I'm just not understanding how to use the IQ files correctly. I could potentially even share some IQ files if that would help.

 

[boatbod]

That is really useful information about needing information from the control channel in order to decode a P25P2 voice channel. I've recently started using @boatbod 's fork of OP25 with success listening to a local trunked P25P2 system. I find myself now in a similar situation, trying to turn recordings of IQ samples later into audio files to listen to. I'm able to listen to the live system using my RTL-SDR and multi_rx.py, but I've now been trying to get it to work off of a recorded IQ file, like a SIGMF file, using this example config. I have example recordings of just the voice channel when it is active, and wider spectrum recordings that include the control channel and the voice channel. I've had no success so far getting any audio out, or better yet, and audio recording. Given what you've said now about needing to know info from the control channel, I'm wondering if there is a way to use the IQ recording that includes the control channel and the voice channel, or some other way to accomplish this task. So far OP25 is the best tool I've found for the job, but I'm wondering if this use case is too niche or likely I'm just not understanding how to use the IQ files correctly. I could potentially even share some IQ files if that would help.

If you use rx.py variant of op25 (single dongle, single receiver) you can do it by starting a symbol capture and replaying it through op25.