DSD+ fastlane gets a lot of error while decoding.

[vini_i]

I started this endeavor with unitrunker and DSD+. I was having issues with a lot of decoding errors. The audio sounded like horrible autotune. It was suggested on these forums to ditch unitunker and go completely with DSD+ Fastlane.

Now I have gone fully with DSD+ Fastlane. Everything seems to be working but I still get a lot of decoding errors. To be clear I get fewer errors with Fastlane than I did before but it doesn't sound great. Almost every transmission has some errors. Usually, the errors just make it sound bad. Some transmissions start off with no errors but then the errors start and the transmission gets completely garbled.

My setup is as follows.
Two dongles. RTL-SDR and a NooElec.
DSD+ Fastlane V2.155

FMP-CC.bat
FMP24 -i1 -o20003 -P0.0 -b9.5 -f858.5125

FMP-VC.bat
FMP24 -i2 -o20002 -P0.0 -rv

CC.bat
DSDPlus -e -fa -i20003 -rc -OM NUL

VC.bat
DSDPlus -fa -rv -o1 -i20002 -OM NUL

I have a feeling that my inexperience just messed up a setting somewhere.
How can I reduce the errors that DSD+ is getting?
Thank you

 

[mtindor]

What type of dongles do you have? Are they <1 PPM TCXO dongles? If they aren't, you are going to have to figure out the amount of drift that occurs in them (after warmed up) and set that drift in FMP24-CC and FMP24-VC.

If you are listening to P25, set bandwidth in FMP (using the 'b' key) to 9.5, or perhaps 12.5 if you are monitoring a simulcast ssystem. If you are listening to DMR/NXDN96, set Bandwidth to 7.6. If you are listening to NXDN48 set Bandwidth to 4.

Also, it could be that you are running your gain too high or two low. You can use the 'g | G' in FMP24 to increase/decrease the gain.

Or maybe the signal just isn't that strong. Maybe post a few screenshots of what FMP24 (both copies) look like when monitoring the system.

 

[n4jts]

What would the 3 batch files look like using fmp and dsd plus with a scanner and a dongle with a p25 faze 1 lsm system.

 

[vini_i]

The two dongles I have are
1. RTL-SDR Blog R820T2 RTL2832U 1PPM TCXO SMA - I've checked the drift with SDR# and it is within 1PPM. SDR# is not capable of adjusting to less than 1PPM.
2. NooElec NESDR Mini 2+ 0.5PPM TCXO RTL-SDR & ADS-B USB Receiver - Same as above.
Is there a better way to adjust them?

I'm listening to P25. The bandwidth in the FMP-CC was already set to 9.5. I assume I should set FMP-VC to 9.5 as well?

 

[mtindor]

The two dongles I have are
1. RTL-SDR Blog R820T2 RTL2832U 1PPM TCXO SMA - I've checked the drift with SDR# and it is within 1PPM. SDR# is not capable of adjusting to less than 1PPM.
2. NooElec NESDR Mini 2+ 0.5PPM TCXO RTL-SDR & ADS-B USB Receiver - Same as above.
Is there a better way to adjust them?

I'm listening to P25. The bandwidth in the FMP-CC was already set to 9.5. I assume I should set FMP-VC to 9.5 as well?

Unfortunately that screen capture isn't big enough / clear enough for me to view. But certainly the signals look fine in the FMP24 windows. I can't read the command prompt windows well enough to see what the error situation looks like. Nothing you are doing stands out as being "wrong" based upon what I can see. What does the CPU usage look like when it is decoding? FMP24+DSDPlus (even two copies) with all TCP linking taking place uses an amazingly low amount of resources (or should) based upon my experience and can run on some pretty minimal setups. But I'd figure I'd ask about CPU anyway.

 

[cg]

Your gain seems high at 40.6
Lower the VC gain during a conversation and see if decoding improves.

chris

 

[vini_i]

Sorry that the screen capture was so poor. I hope these are better.

 

[mtindor]

I don't think it's a gain issue, even though you have gain turned all the way up. Those are 30-40 dB signals. Shouldn't be any errors. I don't think the signals are too "strong." However, for craps and giggles, how about using the "g" key in both FMPs to lower the gain down significantly, maybe to 35 or so. Make note of the signal strength (how high the signal is compared to the noise floor). Lower your gain til your signal itself (as compared to the noise floor) drops. I bet you could at least lower that gain down to 40 without dropping SNR (signal to noise ratio). At the point where you start seeing the signal itself (the height of the signal itself between the noise floor and the peak) start to decrease, then you can stop lowering the gain. But I bet a gain of 35 would work just as well and could potentially clear up any decode issues, if gain is the problem. But again, I don't see how gain would be the problem because it doesn't look like the frontend of the dongle receivers are saturated.

 

[vini_i]

I tried to lower the gain to 30. Here is a before and after captures. It made no difference in the number of errors.

As suggested I also checked the CPU usage. It stays around 16%. It went as high as 20% but that's it.

 

[mtindor]

Ok, at this point I'm out of suggestions. Maybe you can record some raw audio and upload the raw audio somewhere and provide a link, so that the DSDPlus author could then download the raw audio and see what he/she thinks.

To record raw audio, press 'r' inside the DSDplus window. In your case, you'd probably want to press "r" in the VC copy of DSPlus. Then wait until it captures about 30 seconds of actual audio. Then press "r" again to stop the raw recording. Then find the appropriate DSDPlus-Raw-Audio*.wav file in your DSDPlus directory, zip it up, and upload it somewhere and provide the link in the forums. If the raw audio is under 10 MB in size uncompressed, you can probably send it straight to dsdplusfastlane@gmail.com via email if you wanted. But you want to make sure that there is actual voice traffic occurring when you are recording. If it's just recording dead air, there will be nothing for the author to glean from that.

 

[BM82557]

Shouldn't you have an -rc in your

FMP-CC.bat
FMP24 -i1 -o20003 -P0.0 -b9.5 -f858.5125

 

[slicerwizard]

Shouldn't you have an -rc in your

FMP-CC.bat
FMP24 -i1 -o20003 -P0.0 -b9.5 -f858.5125

Won't matter unless the control channel rotates.

 

[vini_i]

I made a screencast of 5 min of both sound and the decoding stream.
Let me know what you think.

 

[cg]

Sounds like $25 radios.
Seriously though, I get similar results. My experience is that female voices decode better, higher pitched ones best. Male voices can break up or clip, especially lower pitched. Sometimes a system can have a weaker channel or one with some slight interference. They all seem decent, although 529 and 689 may have had a bit more clipping. Certain brands of radios can sound a bit better or a bit worse.

chris

 

[slicerwizard]

I didn't see or hear "a lot of error while decoding". Didn't have any problem understanding any of them.

 

[vini_i]

Sounds like $25 radios.
Seriously though, I get similar results. My experience is that female voices decode better, higher pitched ones best. Male voices can break up or clip, especially lower pitched. Sometimes a system can have a weaker channel or one with some slight interference. They all seem decent, although 529 and 689 may have had a bit more clipping. Certain brands of radios can sound a bit better or a bit worse.
chris

If that is what I should expect to hear from a $25 radio then it's fine. This was probably the clearest I've heard it.

That said, how much of an improvement would you get from a more expensive radio?
Such as an Airspy Mini, Airspy R2, or HackRF One. I've been fawning over the HackRF for a while but the $300+ price tag is hard to swallow on a shoestring budget.

 

[dave3825]

I have nooelec and airspy. I do not notice any difference in audio quality.

 

[slicerwizard]

I've been fawning over the HackRF for a while but the $300+ price tag is hard to swallow on a shoestring budget.

I hear that they're deaf. Why waste the money?

 

[LD723]

If that is what I should expect to hear from a $25 radio then it's fine. This was probably the clearest I've heard it.

That said, how much of an improvement would you get from a more expensive radio?
Such as an Airspy Mini, Airspy R2, or HackRF One. I've been fawning over the HackRF for a while but the $300+ price tag is hard to swallow on a shoestring budget.

Does not matter what sdr equipment you get whether its $300 or $25. Audio quality will be the same because you are using the same program aka dsdplus to decode audio therefore audio quality will be the same until they change it in future updates. So in this case sdr's have nothing to do with audio quality, it is the programs you use to demodulate the digital audio that does, aka again dsdplus.

 

[vini_i]

I hear that they're deaf. Why waste the money?

Could you elaborate on what issues the HackRF has? I'm quite new and I know non of lingo.