IP over DVB-S2

  • Hello,

    1) A kind of PACSAT BBS or HamNet access

    as described above...

    About the point 1, a short term solution for IP/Hamnet over QO-100, what do you think about my proposal to port my NPR protocol to QO-100 WB, like described in my previous post? Do you find that it would be useful or not?


    2) A successor for P4-A which would replace the Analog Linear Transponder Downlink by a regenerative digital transponder with a single DVB-S2 downlink.

    About the point 2, it is similar to what P4B, in the USA, planned to do a few years ago.

    In my opinion, it is far from optimal (it's only my opinion):

    - A pure "bend pipe", like QO-100, is much better for experimenters like us, in order for evey motivated OM to experiment new things on his own.

    - The number of simultaneous TX stations is (very) limited.


    Part of the Uplink would be still "linear" as it is for SSB/CW/etc., but just like a remote SDR which will stream the "passband" down as I/Q data on the DVB-S2 downlink.

    Another topic about "point 2" I’ve not understood the "narrow band SDR" that you propose, inside the satellite. If you want to capture 100kHz RF bandwidth at uplink side, then you need more than 24bits x 100kHz= 2.4Mbps for IQ samples of each channel, for 12bits IQ sample resolution, to the downstream. This induces a huge RF bandwidth need at downlink (~2MHz with QPSK) compared to a pure “bend pipe” solution (~100kHz). Therefore, unless I have not understood something, I don’t think that it’s a good idea.


    73, Guillaume F4HDK

  • Another topic about "point 2" I’ve not understood the "narrow band SDR" that you propose, inside the satellite. If you want to capture 100kHz RF bandwidth at uplink side, then you need more than 24bits x 100kHz= 2.4Mbps for IQ samples of each channel, for 12bits IQ sample resolution, to the downstream. This induces a huge RF bandwidth need at downlink (~2MHz with QPSK) compared to a pure “bend pipe” solution (~100kHz). Therefore, unless I have not understood something, I don’t think that it’s a good idea.

    Hi Guillaume,


    you are absolutely right! :/ I did this long ago and did not re-check, only circulated internally where nobody noticed this mistake either :huh: Maybe because we were also thinking in parallel about "virtual channels" with demodulation and regeneration, for example with 2.5 kHz BW and demodulator for SSB, PSK, etc. FM-Uplink, other modes with more BW indeed, etc.. Onboard demodulation would indeed save a lot of bandwidth.


    However, the idea to use a DVB-S2X only Downlink was lately driven by the fact that it would have a lot of advantage over an analog "bent-pipe" transponder. Mainly no need for drift compensation and abuse of uplink power would not have any effect. But it indeed also has disadvantages..


    On the other hand, a "STELLA" kind of Linear Transponder would probably even make more sense for SSB, CW, etc. This concept originally came from Howard Long G6LVB for P3-E and we are currently designing some new Hardware for a LEO satellite.


    But thinking more about it, it would in fact fit very well for a GEO...


    So perhaps a "bent-pipe" transponder with plug-in STELLA functionality and a separate DVB-S2X Downlink, but with DVB-S2 Uplinks and "regeneration"...


    I still need to learn more about NPR, it's protocol etc..


    There is also some development going by our team member Mario Lorenz DL5MLO regarding extremely narrow band DVB-S2X via QO.100, He was able to successfully receive the upper PSK FEC telemetry from the beacon just with an LNB directed to the satellite. So I hope this development can also give additional input..


    STELLA: Satellite Transponder with Equalizing Level Limiting Adapter




    73s Peter

    Peter Gülzow | DB2OS | AMSAT-DL member since 1983 | JO42VG