DVB-S2 as a candidate for Narrowband

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G4GUO
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Location: Worthing

DVB-S2 as a candidate for Narrowband

Post by G4GUO » Wed Jul 03, 2013 11:56 am

I just thought people might like to know that using DATV-Express I have been doing
some tests today using DVB-S2 APSK16 5/6 FEC at 600 KS/s. At that rate I can send
MPEG2 video at 1.4 Mbits and surprisingly my Satlink satellite finder can lock onto it
and display the video. The Satlink won't operate below 600K though. I can see it trying
but it won't lock.

- Charles

F6DZP
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Re: DVB-S2 as a candidate for Narrowband

Post by F6DZP » Mon Aug 25, 2014 4:07 pm

Yes I think we can go down to 100 kS/s. last month we have worked DVB-S using SR= 250 kS/s.
Next step will be DVB-S2 and SR 100 kS/s

Jean Pierre F6DZP

G4GUO
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Re: DVB-S2 as a candidate for Narrowband

Post by G4GUO » Mon Aug 25, 2014 5:00 pm

Hi Jean Pierre,

The only issue was the receiver it would not lock below 600 KS/s.

The sooner we can persuade people to adopt MPEG4 the better :)

- Charles

F6DZP
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Re: DVB-S2 as a candidate for Narrowband

Post by F6DZP » Tue Aug 26, 2014 11:47 am

Hi Charles,

Today I have tested SR 125 kS/s http://www.vivadatv.org/viewtopic.php?f ... p=950#p950

Receiver could lock but we must change value in some registers.
(change of alpha and beta values in PLL..., ask demodulator for decimation of the surplus sample, which avoids saturation of the Nyquist filters at these very low baud rates)
Standard software/driver or firmware don't do that, so limitation for low rates remains.

73
Jean Pierre F6DZP

G4GUO
Posts: 475
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Location: Worthing

Re: DVB-S2 as a candidate for Narrowband

Post by G4GUO » Tue Aug 26, 2014 12:07 pm

Great news Jean Pierre,

Linux supports that card (and the USB2 version of it) so it should be possible to
modify the standard Linux kernel module to do that as unlike Windows all the
source code is available.

One of the problems with us all going digital is that DATV is software and so few
ATVers can write or understand complex software. We need a complete re-skilling
of the community if we have any hope of having a future.

- Charles

F6DZP
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Re: DVB-S2 as a candidate for Narrowband

Post by F6DZP » Tue Aug 26, 2014 12:45 pm

With F5OEO we think to propose for DVB-S modulator : 1 RaspberryPI with software already set on SD card for H264 encoding, giving directly IQ signal, just a little circuit remains to build.
and for DVB-S reciver : 1 rasberryPi with software already set on SD card using USB card like TT S2-3600 or 3650 that is similar to S2-3200 i am using today at 125 kS/s.

It could be a solution ...?

Jean Pierre F6DZP

G4EWJ
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Re: DVB-S2 as a candidate for Narrowband

Post by G4EWJ » Tue Sep 02, 2014 7:12 pm

Linux supports that card (and the USB2 version of it)
Do you have the number of the USB version please?

Brian

G4GUO
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Location: Worthing

Re: DVB-S2 as a candidate for Narrowband

Post by G4GUO » Tue Sep 02, 2014 8:01 pm

TT S2-3600

I think it only supports QPSK and 8PSK though.

- Charles

g4wvu
Posts: 51
Joined: Sat Jun 22, 2013 10:42 am
Location: Colkirk, North Norfolk, UK

Re: DVB-S2 as a candidate for Narrowband

Post by g4wvu » Wed Sep 03, 2014 12:42 pm

G4GUO wrote:I just thought people might like to know that using DATV-Express I have been doing
some tests today using DVB-S2 APSK16 5/6 FEC at 600 KS/s. At that rate I can send
MPEG2 video at 1.4 Mbits and surprisingly my Satlink satellite finder can lock onto it
and display the video. The Satlink won't operate below 600K though. I can see it trying
but it won't lock.

- Charles
APSK16 5/6 FEC is going to want good link margins.......! All very interesting stuff though :)

G4EWJ
Posts: 588
Joined: Wed Feb 17, 2010 10:11 am
Location: Wirral

Re: DVB-S2 as a candidate for Narrowband

Post by G4EWJ » Wed Sep 03, 2014 2:53 pm

Thanks Charles.

Brian

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