SDRTrunk SDRTrunk vs OP25 decoding - very diff performance, why?

[dimab]

summary - in a simulcast system - SDRTrunk audio decoding works way worse than OP25, same antenna, same dongle, diff OS (Ubuntu vs Windows 10), why?

I've been running OP25 and the audio decoding has been excellent (on Ubuntu).
I wanted to try SDRTrunk, so I booted up my Windows machine, moved the dongle (that was used for op25) to this setup, added a second dongle, same antenna setup, same site, SDRTrunk runs fine, config is fine, but the audio decoding is a mess. most transmissions are only half decoded and the rest goes into a digital noise like the decoding isn't working. Any recommendations on possible fixes or changes to my setup?
SDRTrunk is running .5.0-alpha6 (looks to be the latest)

 

[WX4JCW]

It pretty much has to do with how the vocoder is programmed I’ve never had a whole lot of luck with SDRTrunk voice decode, but SDRTrunk has a lot of cool features

 

[dimab]

It pretty much has to do with how the vocoder is programmed I’ve never had a whole lot of luck with SDRTrunk voice decode, but SDRTrunk has a lot of cool features

I'm really hoping I can get this working because all the cool features that it does offer! been listening to it all morning and it's just awful audio.

 

[WX4JCW]

Try adjusting the PPM

 

[wgbecks]

I am an avid user of OP25 and SDRTrunk and have not experienced any audio decoding or quality issues. That said, I can tell you that both programs must have the frequency compensation PPM (Tuner) and LNA gain settings optimized accordingly. Make especially sure that you have setup your P25 Channel for LSM when monitoring Phase-I (FDMA) Simulcast and for all Phase-II (TDMA) systems.

 

[PDXh0b0]

as mentioned ppm and gain, click tuners, select the tuner, bottom right panel, scroll down,the gain is usually at 327, trying different gains I found a value of 279 was best for a tower for our local transit system, that is 14 miles as a crow flies across congested metro and hills. Agian of 327 does get most of it, but I miss calls and some are garbled or cut, with the adjustment I catch 95% of the calls a guy with the same set-up 2 miles from the tower catches.

 

[dimab]

is there documentation on managing multiple receivers? I clearly don't get the finer points of this, but it seems that both RTL dongles are the same ID, and changing the settings like gain or LNA seems to change it for both dongles at once? or at least the way the UI behaves it seems to have change both.

 

[awasser1]

you can add serial numbers to each dongle. I had to google how but it was easy once i followed directions. all mine have a self made s/n with them. if both have the same antenna or similar ones I just put "none" and let the system decide.

Alec
N1AJW

 

[dave3825]

I've been running OP25 and the audio decoding has been excellent (on Ubuntu).
I wanted to try SDRTrunk, so I booted up my Windows machine, moved the dongle (that was used for op25) to this setup, added a second dongle, same antenna setup, same site, SDRTrunk runs fine, config is fine, but the audio decoding is a mess. most transmissions are only half decoded and the rest goes into a digital noise like the decoding isn't working.

What are the specs on the machine and what version of Windows?

Minimum System Requirements

• Operating System: Windows (32 or 64-bit), Linux (32 or 64-bit) or Mac/Linux (64-bit, 10.14 or higher)
• CPU: 4-core
• RAM: 8GB or more (preferred). Depending on usage, 4GB may be sufficient.

I clearly don't get the finer points of this, but it seems that both RTL dongles are the same ID, and changing the settings like gain or LNA seems to change it for both dongles at once?

I have not changed my serial numbers and have no issues.

 

[dimab]

based on a few comments, I've got SDRTrunk working great.
a) enabled auto PPM correction
b) changed the gain until things improved
c) changed the serial number on my second rtl dongle so that SDRTrunk could ID them correctly, used rtl_eeprom -s 00000000 command

 

[awasser1]

What are the specs on the machine and what version of Windows?







I have not changed my serial numbers and have no issues.


View attachment 105043

Yes you need to serialize your dongles or they will all move at once. I have 6gb of ram in an old laptop and windows 7. it works great. another key is good signal strength. You will get it just needs a little adjustment


Alec
N1AJW

 

[dave3825]

Yes you need to serialize your dongles or they will all move at once.

Huh? I don't know about that. I have run 1 nooelec on a 500mhz system and the other on a 700mhz system and have not had any issues.

 

[dimab]

Huh? I don't know about that. I have run 1 nooelec on a 500mhz system and the other on a 700mhz system and have not had any issues.

I think his point was towards using multiple dongles on same computer.

 

[dave3825]

I think his point was towards using multiple dongles on same computer.

I am running multiple dongles on the same computer, 2 nooelec and an airspy. All in sdrtrunk.