DSD FME

[bobruzzo]

OK that might explain....thank you. I dont know much about how DMR works. I tried tuning in to an NXDN48 signal but couldnt get anything on dsd-fme. I live in a suburban area with full scale signals on mostly everything. Not sure how to use the menu in dsd-fme. Confusing. I press ESC then scroll down to pick a mode. But do I also have to go back in and press "resume decoding"? Also the input/output options. Do I need to do anything in there? I am listening to dsdplus on my Windows computer and hearing a lot of both NXDN48 and DMR coming thru. I enter those busy freqs in GQRX but not hearing them. There are a couple of DMR ham repeaters in the area so I will try to see if I can hear anything there.

 

[lwvmobile]

Confusing. I press ESC then scroll down to pick a mode. But do I also have to go back in and press "resume decoding"?

No, not usually, unless you just want to get out of the menu without selecting an option. Usually, you just open the menu, and hit the enter key on the selection you want, and either it'll go back to decoding on its own, or puts you back to the previous menu, just depends on the context of which one you hit enter on.

Also the input/output options. Do I need to do anything in there?

Not particularly. Nothing in there should enable or disable you from listening to decoded audio.

I am listening to dsdplus on my Windows computer and hearing a lot of both NXDN48 and DMR coming thru. I enter those busy freqs in GQRX but not hearing them. There are a couple of DMR ham repeaters in the area so I will try to see if I can hear anything there.

If that's the case, then there still has to be something going on between GQRX and DSD-FME? Could be squelch related, bandwidth related, noise filtering settings in GQRX, feedback loop, don't really know without being able to see what is going on.

Can you send screenshots of your current GQRX setup? Particularly of the Receiver Options with the Mode Options, the Input Controls, and also the VFO on the signal in the waterfall itself? Just trying to rule out every potential issue along the way at this point.

 

[bobruzzo]

I really am not sure how to set all of the MANY options in these programs, but there is no clear directions step by step to do it. Hopefully this helps. The uhf P25 freq I have on there is the local PD channel 1. I saw a few transmissions, and see a good strong signal on gqrx, and on pulse audio playback I see a signal in bar graph but no audio getting to speakers. As far as P25, do I need to set the NAC or does dsd-fme find it? Also to monitor a P25 simulcast system do I need to use a control channel? Our town PD has a stand-alone UHF P25 system, not simulcast. I have it set on dsd-fme to XDMA, so I guess thats right. Last pic is the full scale P25 transmission in gqrx but not getting to speakers! I also have "UDP" selected on gqrx if that is any help. Phase 2 parameters missing??? showed up in the call info section of dsd-fme......just noticed.

 

[bobruzzo]

DSD-fme.....here is current view......I did briefly hear a GARBLED noise at one point but still no audio to speakers. DSD-fme is definitely hearing what gqrx is sending it. looks like the NAC and 2 other things missing! I know the NAC which is "DEF NAC" but unsure of WACN and SYS or where to find them.

 

[lwvmobile]

Wow. First suggestion, turn the Hardware AGC off. That Yellow and noise floor isn't a good thing. I'm kind of suspecting that AGC is overloading things with incoherent sound that nothing would be able to properly decode. You want to have it so that noise floor is towards the very bottom of the FFT window. Then after that, probably a good idea to set squelch so that it won't break on random noise, but will come in clear as day on good signal.





Get the signal and the noise floor to look more like this.

As far as P25, do I need to set the NAC or does dsd-fme find it?

No, it will find the NAC by itself on phase 1 systems.

I have it set on dsd-fme to XDMA, so I guess thats right.

That will do it. XDMA is just a dumb name I gave to the decoding class for P25 1, 2, and DMR BS/MS, kind of like FDMA/TDMA kind of thing.

Also to monitor a P25 simulcast system do I need to use a control channel?

Well, about Simulcast and P25, I haven't been able to thoroughly test that, but in the pulseaudio branch, right now at least, you'll need to manually switch over to PSK mode at the CLI, for Phase 1, that will be with a `-mq` option, but a lot of that is kind of still a work in progress. Also, the Pulse Audio branch doesn't do any sort of trunking, so just landing it on a pure control channel isn't really all that helpful by itself. The dev branch has some very experimental trunking in it, but it might work, might not, depends on the system type and signal stregnth, and a lot of things I don't have good access to unless the wind is blowing in just the right way.

 

[bobruzzo]

OK I turned off AGC, and I dont know how to turn noise floor down! That may be part of problem. And I have to put squelch at about -36 to be just over noise threshold. OK I wont worry about P25 simulcast. But if I can get noise floor down that might be a start, and the p25 parameters missing error.....sorry I am having so much trouble!!!! I had to set my LNA REAL low to 4.0 db to get noise floor down, look at pic.

 

[lwvmobile]

and the p25 parameters missing error

That's caused by a false sync pattern, probably due to all the random noise being pumped into DSD-FME. I'm assuming its because of that, and not you trying to listen to a phase 2 rf channel anyways.

OK I turned off AGC, and I dont know how to turn noise floor down!

You just need to manipulate the LNA gain level and also the sliders in the FFT settings tab. Remembering how to do it in GQRX was more of a pain than I remembered it being.

What kind of SDR equipement do you have? Are you using an RTL dongle, or Airspy, or something else?

 

[bobruzzo]

That's caused by a false sync pattern, probably due to all the random noise being pumped into DSD-FME. I'm assuming its because of that, and not you trying to listen to a phase 2 rf channel anyways.



You just need to manipulate the LNA gain level and also the sliders in the FFT settings tab. Remembering how to do it in GQRX was more of a pain than I remembered it being.

What kind of SDR equipement do you have? Are you using an RTL dongle, or Airspy, or something else?

I am using rtl-sdr dongle hooked up to OMNI X antenna up pretty high with lmr-400 coax. OK Got LNA to lower noise floor. U are right, gqrx VERY annoying to use. Not sure if there is alternative. I like the challenge of getting these things to work in Linux but as you can see it gets drawn out asking for help! OK Maybe I will switch back to DMR...not sure if my town PD P25 is phase 1 or 2.

 

[lwvmobile]

I am using rtl-sdr dongle hooked up to OMNI X antenna up pretty high with lmr-400 coax. OK Got LNA to lower noise floor. U are right, gqrx VERY annoying to use. Not sure if there is alternative. I like the challenge of getting these things to work in Linux but as you can see it gets drawn out asking for help! OK Maybe I will switch back to DMR...not sure if my town PD P25 is phase 1 or 2.

Whelp, time to get rid of the middle man, let DSD-FME use your dongle directly with its built in rtl_fm input. Go ahead and close out of both GQRX and DSD-FME, and try running with this command instead.

dsd-fme -i rtl -c 482.4125M -P 2 -G 36 -D 0 -U 6020 -Y 12 -N 2> log.ans

Just make sure that frequency you want is accurate first, just looking at the photo you sent earlier.

 

[bobruzzo]

Whelp, time to get rid of the middle man, let DSD-FME use your dongle directly with its built in rtl_fm input. Go ahead and close out of both GQRX and DSD-FME, and try running with this command instead.

dsd-fme -i rtl -c 482.4125M -P 2 -G 36 -D 0 -U 6020 -Y 12 -N 2> log.ans

Just make sure that frequency you want is accurate first, just looking at the photo you sent earlier.

Hahahaha ok let me try that!!! Well I ran that after doing what you said but still getting the phase 2 missing parameters error. Also in pulse audio in playback tab, DSD-FME1 : XDMA SLOT 1 on and DSD-FME2 : XDMA SLOT 2 on......

 

[lwvmobile]

Also, I just noticed this photo you sent earlier, I guess I missed it in the sea of yellow, but your PPM level was off in this photo, just a bid wide right. Double check that PPM level as well, I think you had 2.0 on it, might try for 0.

 

[bobruzzo]

Also, I just noticed this photo you sent earlier, I guess I missed it in the sea of yellow, but your PPM level was off in this photo, just a bid wide right. Double check that PPM level as well, I think you had 2.0 on it, might try for 0.

View attachment 131419

OK I will check that too in a minute....I guess not knowing if what I am listening to is phase 1 or 2 isnt helping......and p25 parameters missing sounds like somethings wrong. In pulse audio (playback) does this look right? When I click on the lock it shows all 4 front left/front right? OK running P25 UHF again, changed ppm to "0".....

 

[bobruzzo]

UPDATE.....ok whatever happened it seemed to just work...P25 voice came on loud and clear. I will keep an eye (and EAR) on this for a while. I think the trickiest part for me has always been routing audio.

 

[lwvmobile]

Well, that's something, I really wonder if the PPM was your main issue. Just out of curiosity, what P25 system is that that you are listening to. I want to take a look at the RR database entry for it and get some specifics, see if its just P1, or P1 and P2.

 

[bobruzzo]

Well, that's something, I really wonder if the PPM was your main issue. Just out of curiosity, what P25 system is that that you are listening to. I want to take a look at the RR database entry for it and get some specifics, see if its just P1, or P1 and P2.

It's on THIS PAGE: rr Just scroll down to find the town of Cranston..... Also I noticed the positions of gqrx and dsd-fme on the pulse audio playback tab switches around sometimes...Normally gqrx is on top followed below by dsd-fme......and in gqrx sometimes the output switches from virtual sink back to speakers.

 

[lwvmobile]

Oh okay, well, that does appear to be a trunked system, so I can't imagine you will hear very much traffic by parking on only one of its frequencies. Is that system a simulcast system, or no?

The pulse audio branch doesn't support any sort of trunking, but I have been working on some rudimentary trunking for P25. If you want to switch over to the dev branch, you could try to trunk track that system in particular and see how it works for you with DSD-FME. If it has too many issues due to simulcast distortion (I honestly can't test for this fully), then I'd recommend giving either OP25 (personally recommendation) or SDRTrunk (CPU/Resource Heavy) a shot and see how one of those work out for you.

 

[bobruzzo]

Oh okay, well, that does appear to be a trunked system, so I can't imagine you will hear very much traffic by parking on only one of its frequencies. Is that system a simulcast system, or no?

The pulse audio branch doesn't support any sort of trunking, but I have been working on some rudimentary trunking for P25. If you want to switch over to the dev branch, you could try to trunk track that system in particular and see how it works for you with DSD-FME. If it has too many issues due to simulcast distortion (I honestly can't test for this fully), then I'd recommend giving either OP25 (personally recommendation) or SDRTrunk (CPU/Resource Heavy) a shot and see how one of those work out for you.

Its a stand alone system using P25....It used to run regular UHF FM years ago but they changed to P25 a while back. I can listen on scanner, they have 4 freqs but channel 1 the most active. Its not simulcast. Most of the whole state is on a simulcast system but a few towns prefer to stay on conventional. Hahahaha I remember looking at OP25 a while ago and it looked way too involved for my limited knowledge. What I was wondering is if there is a way to set up "gqrx-scan" to be able to listen to more than 1 freq using DSD-fme. I used to listen to a few conventional freqs a couple years ago using gqrx scan but I dont remember how to set it up. Also I do run sdr trunk on both my linux and WIN pc's. I just like the challenge of getting these things to work on Linux. I attached pic of that setting in gqrx but I dont understand it. I see its set for APT 25 I assume for P25? Do I set it back to APT 17 for DMR?

 

[lwvmobile]

Its a stand alone system using P25....It used to run regular UHF FM years ago but they changed to P25 a while back. I can listen on scanner, they have 4 freqs but channel 1 the most active. Its not simulcast.

Oh, in that case, should be pretty easy to trunk, assuming I got all the right iden_ups and voice grant assignemnts correct in the software, the dev branch should able to trunk with the rtl input or the rigctl to GQRX/SDR++ But again, you say most traffic is on one frequency, I've noticed similar on another P25 system, where the voice priority always seems to go to one frequency, and the other two are used for overflow, but it never seems to get busy enough to use more than one frequency most times.

What I was wondering is if there is a way to set up "gqrx-scan" to be able to listen to more than 1 freq using DSD-fme.

That's funny you mention that, because some of the code in the dev branch for tuning rigctl comes from 'gqrx-scanner' by neural75 on Github. The method I use for looking for a control channel (or just sync) is literally just using snippets of tuning code to cycle through imported frequencies, or frequencies stored in an array from the appropriate P25 PDUs and could honestly be used as is as a make shift digital scanner, albeit one with a 1 second delay between tunes. I've found that trying to run software like gqrx-scanner or just trying to tune rapidly with a dongle isn't going to work well, it needs a very small delay to adjust the noise floor and so on, thus I use a one second hangtime delay as a minimum.

Hahahaha I remember looking at OP25 a while ago and it looked way too involved for my limited knowledge.

Yeah, OP25 does have a steep learning curve, that's for sure. I have a handful of configurations saved, and end up doing a copy/paste and changing things in one or two of them when I want to set something different up. But, if you get it set up and working, it works extremely well.

I see its set for APT 25 I assume for P25? Do I set it back to APT 17 for DMR?

I honestly have no idea. I switched to SDR++ and haven't looked back. I was just going by what another user posted in here quite a while back.

 

[bobruzzo]

Oh, in that case, should be pretty easy to trunk, assuming I got all the right iden_ups and voice grant assignemnts correct in the software, the dev branch should able to trunk with the rtl input or the rigctl to GQRX/SDR++ But again, you say most traffic is on one frequency, I've noticed similar on another P25 system, where the voice priority always seems to go to one frequency, and the other two are used for overflow, but it never seems to get busy enough to use more than one frequency most times.



That's funny you mention that, because some of the code in the dev branch for tuning rigctl comes from 'gqrx-scanner' by neural75 on Github. The method I use for looking for a control channel (or just sync) is literally just using snippets of tuning code to cycle through imported frequencies, or frequencies stored in an array from the appropriate P25 PDUs and could honestly be used as is as a make shift digital scanner, albeit one with a 1 second delay between tunes. I've found that trying to run software like gqrx-scanner or just trying to tune rapidly with a dongle isn't going to work well, it needs a very small delay to adjust the noise floor and so on, thus I use a one second hangtime delay as a minimum.



Yeah, OP25 does have a steep learning curve, that's for sure. I have a handful of configurations saved, and end up doing a copy/paste and changing things in one or two of them when I want to set something different up. But, if you get it set up and working, it works extremely well.


I honestly have no idea. I switched to SDR++ and haven't looked back. I was just going by what another user posted in here quite a while back.

Well I could run sdr++ if I could just get WINE to cooperate but I never had any luck running Windows programs in Linux under WINE.

 

[lwvmobile]

Well I could run sdr++ if I could just get WINE to cooperate but I never had any luck running Windows programs in Linux under WINE.

SDR++ runs natively on Linux, no WINE required.