Issues transmitting DVB-S2 with leandvbtx about leansdr HOT 4 CLOSED

The open issue about self-tests is a trade-off between low SNR and higher-order MODCODS. It's hard to handle all cases equally well. Probably unrelated unless you are trying to do 32APSK.

Another test you can do is leandvbtx->file1 then file1->SDR->RF->SDR->file2 then file2->leandvbrx. This would rule out any realtime performance issue.

Can you show your command lines ? Maybe post a IQ recording of the RX side ?

from leansdr.

Hello,
I tried to pipe the TX IQ into a file, then transmit the file, and also to pipe the RX IQ to a file, then run the demodulator on the file data, with no success.
The command line looks like this:

sudo leandvbtx \
--s16 \
-f 3 \
--standard DVB-S2 \
--modcod 14 \
--roll-off 0.20 \
--rrc-rej 40 \
--buf-factor 2

sudo leandvb \
--u8 \
-f 960e3 \
--sr 256e3 \
--standard DVB-S2 \
--sampler linear \
--ldpc-helper ldpc_tool \
--nhelpers 6 \
--buf-factor 4 \
--gui

Here is an IQ file directly from RTL-SDR. unsigned 8 bit data, 960 kHz sample rate, 256 kSymbols/s 8PSK 3/4 DVB-S2 centered at 0Hz: https://easyupload.io/9mqtir
The resulting Transport Stream should have a bitrate of 570 kbps and should contain only one channel with a static image 640x480 pixels.

from leansdr.

Works for me with "--sr 256060" instead of "--sr 256e3". This suggests that the oscillator frequency error from your SDRs (rx+tx) is about 230 ppm, which is a lot (the default tolerance is 100 ppm). Solutions:

• Specify --sr as above to compensate the oscillator error
• Add "--sr-tol 300e-6" (undocumented) to increase the tolerance to 300 ppm
• Calibrate the oscillator correction factor (hardware-specific).

Besides, I recommend "--sampler rrc" for noisy channels.

from leansdr.

Hello,

Indeed, my SDR had a bug in the software that controls the board clocks, and the frequency was slightly off.
I dug the code and fixed the problem, and now everything works as expected, even in real-time, without changing the tolerance.

Thank you for your help !

from leansdr.