Software DVB-S demodulator

Ok a few tips to make locking to the signal easier:

Getting Timing recovery right is the first step.

There is a Symbolrate Slider that needs to be very close to the actual symbolrate after centering the transponder in the waterfall display. You can check if you have timing lock by watching the symbolrate display at the very bottom of the window. It should stay very close to the sliders symbolrate without drifting away. If it drifts away too much, change the symbolrate slider again, to reset the current value (bottom of screen) to the sliders value, because the slider only affects filtering, but not resampling!

It this is done correctly, the IQ Plot is flashing from time to time. You will see a circle for strong signals, but not more until this point. Timing recovery should work reliably, also for very weak signals.

The next thing to do is to enable carrier recovery in the 'Fine' carrier cecovery tab. If you do this right, you should see more symbols inside the IQ plot. A valid QPSK constellation should also appear. For weak signals, increasing gain and damping can be necessary. If you see the derotated QPSK constellation, you can decrease the gain again.

I'll choose better default settings in the next release.

Hope this helps

Marcel

Hi, it supports DVB-S too, but it's not enabled in this version.

I'll try to make it switchable at runtime in the next version. It has been a compiler flag until now. I think that next weekend is realistic. just working on LimeSDR support.

G8DVR: thanks, great work, i've tried that and it works better atleast.

I'll experiment with that, but looks promising for now.

Ok, there you go! version 2.0.4

- Added LimeSDR support. Tested with LimeSDR Mini.

- Added DVB-S1 support

- Made UDP output address and port changeable

- Minor GUI fixes

http://v.1337team.tk/dvb-s_gui_amsat.zip

Small addition because of the new DVB-S1 feature:

there is a new Skip Symbol button. if you have timing and carrier lock, the next step is to choose the right FEC. after that, skip symbols, and rotate the constellation with the derotate slider, until the sync_confidence value at the bottom of the window increases and stays high. There are two possible derotate settings causing the sync_confidence value to go up, but only one of them works. they are 180° apart.

k, that should explain a lot No auto-lock feature yet. Still have many more things to improve.