some thoughts about DATV on QO-100

After having setup my narrowband equipment a few years ago I had the goal of operating wideband (DATV) too. With my existing Kuhne downconverter and the BaMaTech feed with 2 outputs for 10GHz it was easy to connect a SMA coaxial relay directly near the feed to switch polarization by the switching output of the downconverter. Connecting an ELAD E-Tiouner, powered with about 18-20V input voltage (input voltage = output voltage on F-connector) makes the downconverter switching to the correct LO frequency (9240MHz) and triggering the switching output to ground that makes the coaxial relay switch to horizontal polarization. Using the MiniTiouner software provides the possibility to decode even low symbol rates (from 66kS) and quickly switching of frequency and all other necessary parameters according to what you see in the wideband spectrum.

The TX topic is slightly more complex. There are a few approaches to generate a DVB-S2 signal in a „cheap“ way. First of all I want to clarify that I do respect all the work done by these developers that were involved in all of those projects (e.g. F5OEO, IS0GRB, F5UII – only to mention a few).
During some weeks of trying to find a reasonable, stable and convenient solution to modulate the DVB-S2 signal I was gleaning a lot how others solved this. Software solutions like DATV-Easy, DATV-Express, Portsdown, etc. together with the ADALM Pluto or LimeSDR appear everywhere. I tried every of them with more or less satisfaction. F5OEO’s solution (PlutoDVB) of using the Pluto with a special firmware to receive a RTMP or UDP stream and encode it into DVB-S2 is not bad from the start. The versioning disaster and the different patches don’t make it very easy to find an all-working and reliable version. As I saw, many operators only concentrate on generating glamorous content but not fixing basic issues. How and with the help of which software or encoder the video stream is generated is only secondary in my opinion.

After many weeks I personally came to the conclusion that I want to have a better (maybe the luxury) version for me, and started to investigate which possibilities of commercial DVB-S2 modulators exist.
The parameters: direct output frequency 240xMHz without the need of converting anything, the ability to use low symbol rates, an output power that is able to drive the next stage PA (around +15dBm) and the use of several input streams (UDP, RTSP, etc.) together with a possibility to stream a fixed TS file.
The object of desire: Rohde & Schwarz SMCV100B with the SMCVB-K167 / SMCVB-K519 options.

Some of those reading this might think that it’s a crazy and expensive solution – indeed it is! – but it is not more crazy than operating an IC-7851 or a PT-8000 for shortwave… 😉

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Datum: Mittwoch, 15. Februar 2023 23:28
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