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Using software defined radios I can generate and demodulate a DVB-S2 signal live. I'm wondering if I can use this to send single pictures over the air using as narrow BW as possible. Using QPSK and a symbol rate of 1 MSPS the signal is about 1 MHz wide, which isn't very practical. If I reduce the symbol rate, will the signal occupy less bandwidth?

DVB-S2 Signal

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  • $\begingroup$ why is 1 MHz not very practical? DVB-S2 is meant for satellite channels, and these are not narrow. $\endgroup$ – Marcus Müller Jun 4 at 19:27
  • $\begingroup$ Not practical for ham radio because there's not a lot of BW available until GHz range. I'm thinking UHF. Using DVB-S2 because it has great features like multi rate LDPC $\endgroup$ – nickhansenrf Jun 4 at 19:33
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    $\begingroup$ End use case is a ham satellite on UHF. Lots to learn :) $\endgroup$ – nickhansenrf Jun 4 at 19:40
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    $\begingroup$ Oh, then S2 is of course the right mode! I guess the satellite will be relaying earth-generated signals? $\endgroup$ – Marcus Müller Jun 4 at 19:43
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    $\begingroup$ Payload is a HD camera, so images and maybe videos, if we're allowed and capable. S2 has patents still so I am not sure. $\endgroup$ – nickhansenrf Jun 4 at 19:52
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I've heard that 2 days in the lab can save 2 hours of reading but in this case it turned out to be easy to test. It is the sample rate of the SDR which changes the bandwidth of the signal. Since I am using the PLUTO SDR I can't go below around 500ksps. So I tried with a symbol rate of 300 kbaud at a sample rate of 600k. Able to demod successfully. I asked because I thought this would be harder to figure out but I'll leave it for reference. enter image description here

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  • $\begingroup$ That's not really the point though – if you just scale the sample rate, you're not generating a DVB-S2 signal anymore. Instead, parameterize the encoder so that it uses a lower bandwidth. That's possible with S2! $\endgroup$ – Marcus Müller Jun 4 at 19:25
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    $\begingroup$ Since I scaled both the baud rate and sample rate I think that's what I did. Not super familiar with the standard, or the implementation of this flow graph. I'd actually like to go narrower, and since it's QPSK I think it's just the baud rate that determines BW. But the PLUTO SDR is limited. $\endgroup$ – nickhansenrf Jun 4 at 19:39
  • $\begingroup$ @nickhansenrf If this works for you, then kindly mark your answer as accepted. Also, you seem like a sharp fellow, and we look forward to seeing more of you here on hamSE! $\endgroup$ – Mike Waters Jun 4 at 20:00

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