Posts by F8ACB

  • Software DVB-S demodulator

    Hi,

    I started to test how to decode DATV with this software, and I was able to decode a 333ks/s flow with my RTL2838 and with some help from Luc, ON7KEC.

    Sounds very interesting and really a good job.

    Unfortunately, I got some trouble as beginner to got a proper constellation and to quickly increase the confidence synchro.

    I used some snapshot found on this forum, but it still difficult to find a smoke tutorial / howto from coarse tuning till fine tuning :)

    The baseband processing sounds pretty clear to me and I understand that the software will drive the LNA, I / Q parameters and correction.

    Therefore, at least few questions...

    - I used for a 333ks/s a Kp of 1/16 and Ki of 1/16384 as timing recovery info : I guess that depending on the symbol rate and eventually modulation type, we could consider associated suitable values (and which one)?

    In other case, based on the sample rate, how can we "tune" this parameters (debug stats / plots) ?

    - For the carrier recovery, I usually starts with high values of Kp (i.e 15.57) and high value of Ki (i.e. 0.250); when the software starts to synchronize, I'm reducing these parameters in order to optimize the IQ plot.

    Is it the way to proceed (it's a bit tricky there :/) ?

    - Regarding equalizer section, with lower Taps and Gainu values sounds to give good results.

    Could someone clarify these questions or provide me relevant links ?


    73, F8ACB Samuel