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Raspberry Pi as digital DVB-S TV transmitter

I settled on a final design for a very simple digital TV transmitter for the Raspberry Pi The block diagram:

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The circuit diagram:

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The test board:

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Not all chips are used for this, the AD9761 and AD8346 just forget about them, it is an other project.

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On the Raspberry runs the latest ts2iq_pi software I wrote, source code here:

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Also I wrote Linux some code that supports the STV0299 chip to provide some of the same functions the MS windows Tutioune program has, here it shows the Hauppauge wintv Nova locked to a Raspberry Pi transmission.

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I will make this source available later, make a package for Linux, but it will only be of use if you have a budget PCI card with a STV0299 chip...

About the block diagram, I use 2 small FIFOs (4kx9 each) feeding into a 2x4 to 1 demultiplexer to get IQ from IQIQIQIQ. The symbol rate generator is a transistor 6 MHz crystal oscillator followed by a 4040 counter to make 1500k symbols per second. A 100 MHz crystal oscillator module drives 2 74F74 flips flops to make 2 90 degrees shifted carriers at 25 MHz. This is filtered by a simple LC circuit, and then fed to a small ring diode transmitter, so this makes a 25 MHz exciter. The 180 degree flipping of the I and Q by the modulation is done with 74HC86 XOR gates.

In this setup I used a GPS VCO, 15754200, mixer adds 25 MHz, this gives 1600420000 Hz, sat receiver adds 9750000000, so I tuned to 11,350,42,000 for reception. Of course for the amateur band you need a VCO that is 25 MHz offset of that frequency, and maybe some extra filtering.

Anyways the reason for the setup with the XOR gates and 25 MHz is that it is much less problematic to make a good 90 degrees phase shit than when doing it at a GHz or so.

Important is now the filtering of the VCO supply can control voltage, add a PLL (prescaler with UBP1505 is already on this board). I found my earlier problems with reception came from high phase noise caused by me forgetting to decouple the VCO tuning voltage and supply, not by the low symbol rate, the xdipos software I wrote helped me find that in a way.

I have send some short movie over the wired link (coax directly into the DVB-S card) with this, and it came out perfectly.

I hope this simple design and software will help somebody get started on the Raspberry, cost should be really low this way.

Reply to
Jan Panteltje
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It would be very neat if this could be ported to the Pi...

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(somewhat unlikely I fear)

Theo

Reply to
Theo Markettos

On a sunny day (03 Jul 2013 12:15:34 +0100 (BST)) it happened Theo Markettos wrote in :

That is very old, and not of any practical use. On top of that he does not release source, and it _could_ only display a still picture with _some_ graphics cards.

The real ground stones were put down here:

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Later followed by a much simpler hardware design:

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I have taken that and further simplified it.

As there was no transport stream to IQ software for Linux like (TS188ToIQ.exe for MS windows), and nobody releases source (you can buy the IP for many $$$ from several companies), I wrote my own ts2iq, originally for the PC, then ported it to the Raspberry as ts2iq_pi, and most important I release source so others can build on that. Forget about bellard's, it is nothing.

What I am curious about is if the Raspberry Pi has enough processing power to get real time pictures from the new camera, and drive this DVB-S transmitter hardware at the same time. I do not have that camera yet..., but I think H264 maybe if done with hardware acceleration on the Pi could leave enough cycles, not sure.

Reply to
Jan Panteltje

I have - very unofficially and in a hand wavey sort of way - found that the real power usage comes from DISPLAYING pictures. Especially things like resizing. interpolation and de interlacing.

Not handling mpeg streams or even decoding them. In the days when I used my on-board intel chipset on my (linux) PC,, graphics were dog slow and full screen flash simply did not work.

Getting a graphics GPU card installed changed things completely.

The PI has plenty of grunt for all but displaying big fast moving pictures. It needs a good GFX driver for the onboard video system.

--
Ineptocracy 

(in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
Reply to
The Natural Philosopher

On a sunny day (Wed, 03 Jul 2013 14:32:18 +0100) it happened The Natural Philosopher wrote in :

I got a license key from Raspberry, and it plays HD movies I recorded from satellite like 720 progressive without a glitch. I watched 'Astronaut Farmer' on it a while back, full length.. flawless, very nice. And that is on a big 46 inch where you see any artifacts... So I have one raspi for TV and one for experiments like this :-) Maybe one day I will need a second license key for this one.

The only thing that could be a lot better is the USB... it misses key strokes on my USB wireless keyboard, so I always use it from the laptop or other PC via ssh -Y for programming, ethernet does not have that problem it seems.

I think that also rules out USB webcams, I tried my Logitech E2500, and it does not work right. So that is also why I am curious as how that new camera behaves that is directly connected to the board if I understand correctly.

BTW I am making a web site for the Raspberry DVB-S transmitter and software, work in progress:

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Beware, large pictures.. bandwidth.

Reply to
Jan Panteltje

Is there a reason why you developed this for DVB-S rather than DVB-T/T2 or ATSC?

There is a demand for a cheap digital terrestrial TV sender, even one that produces a multiplex with a single TV service.

--
Graham. 

%Profound_observation%
Reply to
Graham.

On a sunny day (Wed, 03 Jul 2013 19:24:45 +0100) it happened Graham. wrote in :

For me it is just an electronic project, something I can add to 'I can, I did', one of many, and it helps others learn and venture into science, I have seen several of my projects been taken up. DVB-S came along as the system is relatively simple, yet enough of challenge that very few write that soft, and do all of it (hardware and software). On top of that my interest in satellite, and that even goes as far as wanting to know what sort of modulation system aliens (other planets with smart or smarter than us life, and maybe even better TV programs) would use for modulation systems. DVB-S is for example basically the same system (QPSK, FEC, Reed Solomon) as used to communicate with the Voyager spacecrafts. The digital amateur world now communicates via a version of DVB-S with the ISS (International Space Station), and there are challenges too.

If you say 'hey I want a simple DVB-T transmitter', sure recently a guy is selling a USB stick for IIRC 125 $ that does just that:

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(There are more links about that on the web and youtube videos too). In fact it is my experience that in this world you can probably buy anything, or have it invented. But for me it is more fun (and I am not THAT rich that I could buy anything) to design stuff, new things often come from that,. From a financial POV sure 125 $ for an USB stick is probably less then I did spend buying parts not even counting the hours writing software, but it would have been less fun. I mean any person can buy a car, but to design and build your own is satisfying too.

Reply to
Jan Panteltje

HiJan, A noob question . When you say DVB-S transmitter ..is it transmitting all t he way to satellites ? How is it different from DVB-T that transmits in UHF which I can understand ( lot of projects on this that use some sought of R TL-SDR ) ..but this DVB-S term is confusing me Thanks

Reply to
vineethupadhya

DVB-S, DVB-S2 and DVB-T are all digital TV transmission standards. The "S" variant is designed for satellites, where weak signals and rain fade are the problem, the "T" variant for terrestrial work where multi-path reception and, perhaps, man-made interference are the problems. A typical satellite transponder is a "turn-round" device, so DVB-S will be sent up to the satellite on one frequency and retransmitted back to earth on another.

The sticks folk use are for DVB-T, although the majority of SDR is using a "test" mode left in one of the chips where signals are sent straight to the PC rather than being decoded in the dongle.

--
Cheers, 
David 
Web: http://www.satsignal.eu
Reply to
David Taylor

I wonder what percentage of sold DVB-T sticks are used for TV viewing, and what percentage is used for SDR.

When there is a good amount of sticks used for SDR it could be worthwile to develop a stick with performance optimized for that use case.

(I do know about the Funcube Dongle but it has a much smaller bandwidth than the RTL DVB-T stick)

Reply to
Rob

Help please! WTF is SDR?

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Chris Elvidge 
England
Reply to
Chris Elvidge

software defined radio, a technique that allows a computer to "tune" to many transmitters at once, by sampling a relatively large swathe of the RF spectrum.

There are plenty connected to the internet which allow multiple visitors to each "hear" different frequencies.

Reply to
Andy Burns

There are already quite a few SDR assemblies which use the same tuner chip and perhaps a better ADC (analog digital converter) with more bits. They range from the very crude to the quite sophisticated. They are all wideband devices. One example:

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Cheers, 
David 
Web: http://www.satsignal.eu
Reply to
David Taylor

Thanks.

I use my DVB-T tuner to listen to and record Radio4/Radio4x on a Raspberry Pi.

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Chris Elvidge 
England
Reply to
Chris Elvidge

Well there are many more exiting stories on websites than really existing hardware devices. For example, the device you mention has only just moved from the vaporware stage into the "first production". It certainly looks insteresting!

Reply to
Rob

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