DVB-S From a Raspberry Pi with No Extra Hardware

An exciting aspect of the trend in single board computers towards ever faster processors has been the clever use of their digital I/O with DSP software to synthesize complex signals in the analogue and RF domains that would previously have required specialist hardware. When we use a Raspberry Pi to poll a sensor or flash an LED it’s easy to forget just how much raw processing power we have at our fingertips.

One of the more recent seemingly impossible feats of signal synthesis on a Raspberry Pi comes from [Evariste Courjaud, F5OEO]. He’s created a DVB-S digital TV transmitter that produces a usable output direct from a GPIO pin, with none of the external modulators that were a feature of previous efforts required. (It is worth pointing out though that for legal transmission a filter would be necessary.)

DVB is a collection of digital TV standards used in most of the world except China and the Americas. DVB-S is the satellite version of DVB, and differs from its terrestrial counterpart in the modulation scheme it employs. [Evariste] is using it because it has found favor as a digital mode in amateur radio.

This isn’t the first piece of [F5OEO] software creating useful radio modes from a GPIO pin. He’s also generated SSB, AM, and SSTV from his Pi, something which a lot of us in the amateur radio community have found very useful indeed.

We’ve covered digital TV creation quite a few times in the past on these pages, from the first achievement using a PC VGA card almost a decade ago to more recent Raspberry Pi transmitters using a USB dongle and a home-built modulator on the GPIO pins. Clever signal trickery from digital I/O doesn’t stop there though, we recently featured an astoundingly clever wired Ethernet hack on an ESP8266, and we’ve seen several VHF NTSC transmitters on platforms ranging from the ESP to even an ATtiny85.

Thanks [SopaXorzTaker] for the nudge to finally feature this one.

19 thoughts on “DVB-S From a Raspberry Pi with No Extra Hardware

      1. Yep QPSK. And the symbolrate is only around 250ksps. So 250kHz 3dB bandwidth, or 320kHz bandwidth.

        With 7/8 FEC, gives a 403.186275 KBit/s transport stream bitrate.
        With 1/2 FEC, gives a 230.392157 KBit/s transport stream bitrate.

    1. End-to-end latency: I experienced this myself last fall at a booth at Surplus Party Zofingen (HB9): from jumping in front of the camera until I saw myself on the Rx-Screen nearby _several_ minutes passed by.
      (can’t tell where in the chain the big’hunk’o’delay takes place: the encoding on the RasPi or maybe also on the (unspecified) Rx…)

    1. Agreed – DVB-T would be useful. A colleague’s been looking for something to extend the output from a set-top box in one room to another, without using massively long HDMI cables.

    2. Yeah, there is a company called Hides that makes affordable DVB-T hardware. oe7dbh did a lot of stuff with it, if you search for his callsign and ‘Hides DVB-T’ or something you should find some stuff.

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