DVB-T 6, 7 or 8 Mhz Channels ?

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M0DTS
Posts: 685
Joined: Sun Feb 24, 2008 9:03 pm

Re: DVB-T 6, 7 or 8 Mhz Channels ?

Post by M0DTS » Fri Aug 31, 2012 12:40 pm

Excellent news Charles,

I bypassed the original software stage with my Realtek dongle going straight for the sdr software, never even thought to check it out.
Will be interesting soon to be able to compare DVB-T and DVB-S for similar bandwidths on a weak signal path to see what the result is.
I noticed the TX settings you had were qpsk, is DVB-T multiple qpsk signals in a mux? (i've never read up about DVB-T much!)

Rob

G4GUO
Posts: 729
Joined: Tue Feb 16, 2010 12:51 pm

Re: DVB-T 6, 7 or 8 Mhz Channels ?

Post by G4GUO » Fri Aug 31, 2012 1:32 pm

Hi Rob,

Yes all the information carriers have the same modulation in DVB-T.
The parameters I chose were arbitrary, the software supports all
the different modes except SFN
http://en.wikipedia.org/wiki/Single-frequency_network.

I wanted to get the thing to work with Linux but to no avail. It
works fine with the SDR software but no /dev/dvb devices are
created even though dmesg can see the device. A Google
search seems to show I am not the only person having this problem.

- Charles

M0DTS
Posts: 685
Joined: Sun Feb 24, 2008 9:03 pm

Re: DVB-T 6, 7 or 8 Mhz Channels ?

Post by M0DTS » Sat Sep 01, 2012 4:58 pm

Thanks for the info,

I was not aware the carriers could be QPSK, thought they were always QAM!

I've only had the SDR drivers working in Ubuntu, not tried to get it up as a dvb device... will have a look here next time i boot Linux.

Rob

G4GUO
Posts: 729
Joined: Tue Feb 16, 2010 12:51 pm

Re: DVB-T 6, 7 or 8 Mhz Channels ?

Post by G4GUO » Sat Sep 01, 2012 6:17 pm

Hi Rob,

Yes they can be QPSK, 16 QAM or 64 QAM.

I think there is a fix for Ubuntu but I am using Fedora :(

I have been playing with HD today. I am using a PVR-HD
to generate the video and audio. It works OK but I had
to re-scan the channel to get Blaze to figure out it
was getting H.264 instead of MPEG2. My Atom PC
is a bit slow decoding HD :( .

http://2.bp.blogspot.com/-r-Kgu3GVxeA/U ... t_test.jpg

My program is even showing up in the EPG :) .

- Charles

G4GUO
Posts: 729
Joined: Tue Feb 16, 2010 12:51 pm

Re: DVB-T 6, 7 or 8 Mhz Channels ?

Post by G4GUO » Thu Sep 06, 2012 11:20 am

G4GUO wrote:When I am feeling enthusiastic I might try it with a DATV-Express board.

- Charles G4GUO
I tried that this morning and yes I can send DVB-T using the Express board and then
receive it with the Newsky TV Dongle all on 23 cms. The CPU load is much lower
(25%) than when I use the USRP2 as I have moved the interpolater code from the PC
to the FPGA on the Express board.

- Charles

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