Choppy DMR from DSD+ ???

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Murphy625

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I'm using DSD+ and SD Sharp and found some very strong signals up in the 430 something Mhz band. Its actually one very strong signal that's always on and no speech comes from it.. then a second equally strong signal that decodes to speech occasionally, and four or five weaker signals (but still strong) that pop in and out on different (but close) frequencies like the little hammer and monkey game at the carnival. These signals are active 6 days a week and I believe they are all related. Seems like one or two base stations and four or five mobiles or HT's.

When running DSD+, it does decode them, but the speech I'm hearing is very choppy, almost like its not breaking squelch (even with squelch off). Again, the signal strength is really strong and peaks at 0db on the spectrum.

I only hear every other word most times.

Any idea on what's wrong? I'm on a Core i5 computer so I doubt its processing power.

I just started playing with DSD+ so it could be a newbie mistake too..
 

thewraith2008

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Does this happen to other DMR networks you listen too?

Could be a few things:

Your dongle PPM is not set correctly.
SDR# not set to NFM and bandwidth not 12500Hz.
SDR# Audio "Filter Audio" is checked (Best unchecked).
Audio out to DSD+ is not clean (something else mixing with signal?).

If possible set-up DSD+ to use FMP/24/A (via TCP)

What DSD+ version you using?
 

Murphy625

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Does this happen to other DMR networks you listen too?
Don't know.. its the only digital signal I found so far. I'm in a very rural area.

I did lock on to a few others over the past few days but they weren't active for long enough and never repeated.

Could be a few things:

Your dongle PPM is not set correctly.
SDR# not set to NFM and bandwidth not 12500Hz.
SDR# Audio "Filter Audio" is checked (Best unchecked).
Audio out to DSD+ is not clean (something else mixing with signal?).

If possible set-up DSD+ to use FMP/24/A (via TCP)

What DSD+ version you using?

PPM is set to zero and seems correct. When I go to the NOAA Weather stations, I just plug in the frequency and the graph is showing it to be spot on when zoomed.

SDR# is set to NFM and I've played with bandwidth from 12500 all the way up to 14000 but there was no improvement.

I don't even know what FMP/24/A is. You want me to send the signal through my network connections?

Filters are always set to off when I try something new.. Feel free to ask how and why I learned to do that! LOL

Audio going to DSD is straight from "Stereo Mix" driver setting.. I'm forced to listen to both the raw signal from SD Sharp and the DSD+ output at the same time. Could that be the problem?? Could the decoded speech be going back through some loop and being added to what DSD is decoding?

I'm using DSD+ 1.01pt. Its whatever the latest version is as of last week.
 

thewraith2008

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I don't even know what FMP/24/A is. You want me to send the signal through my network connections?

FMP.exe or FMPA.exe is the other half of the DSDPlus (DSD+) package you downloaded.
FMP.exe is the one to use unless you use an airspy then use FMPA.exe.

FMP24 is the fastlane version. (You don't have)

It is the tuner part. Like SDR#. But it connects to DSDPlus via TCP (loopback 127.0.0.1) port. Not over network, just local.


Audio going to DSD is straight from "Stereo Mix" driver setting.. I'm forced to listen to both the raw signal from SD Sharp and the DSD+ output at the same time. Could that be the problem?? Could the decoded speech be going back through some loop and being added to what DSD is decoding?

Yes this is most likely the issue as the output is been feed back into the input corrupting the signal.

I'm using DSD+ 1.01pt. Its whatever the latest version is as of last week.

DSDPlus is available as two versions. Public release 1.101 (The one you have) and Falstlane version (paid). See the end of DSDPlus.txt for more information on this.

You will need to make/modify up to 4 batch files to use DSDPlus/FMP correctly.

Link to a post that shows the example of the 4 batch files needed Just change FMP24 for FMP.

If you really what to stick with SDR# as tuner source then look at getting a "virtual audio cable" as mentioned.

For trunking you generally need 2 dongles and 2 x FMP, 2 x DSDPlus running.

It really comes down to what it is your listening to and how large network is.
 

Murphy625

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I've tried everything and I get the same crappy results.

Tried the FMP, was able to lock onto a signal, same choppy audio.. I hear 1/2 of every other word if even that much.

Installed the virtual audio cable, no change.. I have to set the record/playback defaults in windows just to get it to work and then nothing else works! (can't even begin to describe how annoying that is).

The DSD+ interface and the FMP produce the same results... choppy audio, a few syllables here and there, and occasionally several words strung together.. and its always very muffled.

I found signals in the 440 Mhz band and up in the 850 Mhz range and both do the same thing.
 

Murphy625

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My ppm is set to Zero ( 0 ) and I do not believe it needs to be changed.

When I dial in NOAA weather stations, they're dead center.. Same with band edge spikes and various other known good signal frequencies.
 

slicerwizard

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I'm using DSD+ and SD Sharp and found some very strong signals up in the 430 something Mhz band. Its actually one very strong signal that's always on and no speech comes from it.. then a second equally strong signal that decodes to speech occasionally, and four or five weaker signals (but still strong) that pop in and out on different (but close) frequencies like the little hammer and monkey game at the carnival. These signals are active 6 days a week and I believe they are all related. Seems like one or two base stations and four or five mobiles or HT's.
Sounds more like a trunking system.


When running DSD+, it does decode them, but the speech I'm hearing is very choppy, almost like its not breaking squelch (even with squelch off). Again, the signal strength is really strong and peaks at 0db on the spectrum.
So you're using too much RF gain and overloading the dongle. Might want to start with that.
 

Murphy625

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Sounds more like a trunking system.


So you're using too much RF gain and overloading the dongle. Might want to start with that.

So I took your advice and turned down the gain.. Still no change.. The voices I'm hearing are still very choppy and very muffled like they're talking through a towel or something.

I'm wondering if this could be an issue with my antenna since I'm using a 40 meter dipole to listen to 2 meter and 70cm signals.
It works great for normal analog signals.. clear as can be.. But maybe its an issue with the digital?
 

M105

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Murphy:
Try this...
I assume you have a .bat file to run DSDPlus. Create another .bat file to run it and give the process High CPU priority. Use the double quotes exactly as shown below and replace YourDSD.bat with your filename.

start "" /High "YourDSD.bat"
 

thewraith2008

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What dongle are you using, whats its bandwidth.
You maybe having an issue with dropped packets if you are using a setting that's to high.

Most dongles are 2.4Msps and most PC USBs can generally handle this.
Higher rates maybe an issue.
Other devices on the USB can (and most likely are) causing issues.

You can test with RTLTool
Short write up on RTL-SDR here.
 
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