[Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter

[Vincenzo Pellegrini]

Sure rafael. I'm also looking forward to be able to buy my own WB50...
Is it availale yet? If not, you know when will it be?

2008/11/12, rafael2k <address@hidden>:
> Hello people,
> I'm following the discussion about the Soft-DVB, and I'm thinking about use
> of
> the WBX0510 daughterboard (50 MHz to 1 GHz) w/ Soft-DVB - Will then be
> possible to transmitt in any VHF/UHF channel?
>
> Bye,
> Rafael Diniz
>
> Em Tuesday 11 November 2008, Vincenzo Pellegrini escreveu:
>> Martin ,
>> sorry for the delay. My exams seem to have gone well even if it's not
>> official yet. I also had to do a demo for a company I have a temporary
>> contract with for developing some gnuradio based gsm-r security
>> sentinels. Also the demo was smooth. (i already listed the project on
>> the gnuradio wiki)
>> so i really hope i'll be able to prepare the 8Mhz stream for you
>> within the next 2/3 days. Would this still be useful?
>>
>> 2008/11/3, Martin DvH <address@hidden>:
>> > On Mon, 2008-11-03 at 14:13 +0100, Martin DvH wrote:
>> >> ________________________________
>> >>
>> >> > Van: address@hidden
>> >>
>> >> [mailto:address@hidden
>> >> Namens Vincenzo Pellegrini
>> >>
>> >> > Verzonden: maandag 3 november 2008 0:16
>> >> > Aan: Martin DvH
>> >> > CC: discuss-gnuradio
>> >> > Onderwerp: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter
>> >> >
>> >> >
>> >> > This is Great... :)
>> >> >
>> >> > Yup, the playback cannot be smooth because of the wrong throughput,
>> >>
>> >> definitely.
>> >>
>> >> > Did you use the USRP1 with interpolation factor = 16 ?
>> >>
>> >> Yes I did.
>> >>
>> >> > I can prepare a modulated signal with the correct throughput for
>> >>
>> >> you.. this is not a problem... :)
>> >>
>> >> Please do, this would be great.
>> >>
>> >> > what hard disc are you playing your signal back from?
>> >>
>> >> Internal 2.5" harddisk of my acer 6930 notebook (Aspire 6930G-734G32BN
>> >> LX.AVB0X.135)
>> >> 2.5" 320GB HDD 5400rpm, SATA
>> >
>> > I checked now. It is a:
>> > Western digital Scorpio 320 GB SATA (WDC WD3200BEVT-22ZCT0)
>> > 2.5-inch SATA Hard Drive 320 GB, 3 Gb/s, 8 MB Cache, 5400 RPM
>> >
>> > Benchmark from tomshardware (h2benchw 3.6):
>> > http://www.tomshardware.com/charts/2-5-hard-drive-charts/Minimum-Read-Tra
>> >nsfer-Performance,687.html minimum read transfer rate 33.5 MB/sec
>> > average read transfer rate 52.2 MB/sec
>> > maximum read transfer rate 68.2 MB/sec
>> >
>> >> I am not at home right now So I can't check the exact brand and model
>> >> of
>> >> the
>> >> harddisk.
>> >> It can do around 38 MB/sec so this is just enough (required 32 MB/sec)
>> >>
>> >> I also have 4GB of memory in this notebook, so I think it will buffer
>> >> the complete file.
>> >>
>> >> I had to use my notebook because with my desktop PC (ASrock
>> >> 939-DUAL-SATA2)
>> >> The USB TX bandwidth is less then 32 MB/sec.
>> >> (Which is strange because I CAN receive 32 MB/sec)
>> >> I get UuUuUu on this machine when useing interpolation 16, so unusable.
>> >>
>> >> Regards,
>> >> Martin
>> >>
>> >> > regards
>> >> >
>> >> > vincenzo
>> >> >
>> >> >
>> >> > 2008/11/3 Martin DvH <address@hidden>
>> >>
>> >>           Hi,
>> >>
>> >>           > > In fact: 8 complex Msps implement a 7 MHz channel while
>> >>
>> >> 9.142857143
>> >>
>> >>           > > complex Msps implement an 8 MHz channel.
>> >>           > > Just try to go as close as possible to such sampling
>> >>
>> >> frequency by
>> >>
>> >>           > > using USRP2 and let me know what happens... it could
>> >>
>> >> turn out that we
>> >>
>> >>           > > need a resampler block.
>> >>           >
>> >>           > So if I use a fractional rate resampler with interpolation
>> >>
>> >> factor
>> >>
>> >>           > 10/8=1.25 I get a 7 Mhz channel with 10 Msps samplerate.
>> >>           > If I use a fractional rate resampler with interpolation
>> >>
>> >> factor
>> >>
>> >>           > 10/9.142857143=1.09375 I get a 8 Mhz channel with 10 Msps
>> >>
>> >> samplerate
>> >>
>> >>           > If I use a fractional rate resampler with DECIMATION
>> >>
>> >> factor
>> >>
>> >>           > 9.142857143/8=8/7=1.142857143 I get a 8 Mhz channel with 8
>> >>
>> >> Msps
>> >>
>> >>           > samplerate with the out-of-band skirts folded back at the
>> >>
>> >> sides.
>> >>
>> >>           > Would be interesting to see if this last one works with a
>> >>
>> >> USRP1.
>> >>
>> >>           > I'll let you know how the experiments go.
>> >>
>> >>           I resampled and scaled your ofdm_40.dump file so it now will
>> >> use 8 Mhz bandwidth with a 8 Msps samplerate.
>> >>           The reception never can be perfect this way but it seems
>> >> good enough for
>> >>           tests.
>> >>
>> >>           My USB DVB-T receiver receives the transport stream without
>> >> problems.
>> >>           Mplayer playes the stream without problem for two loops and
>> >> then crashes
>> >>           with a broken frame.
>> >>           My standalone settopbox DVB-T receiver now also receives the
>> >> stream.
>> >>           (8 MHz channel on UHF)
>> >>           It has big problems displaying it. Sound is only a chop of
>> >> sound now and
>> >>           then and video stops, then runs for a second, then stops
>> >> again.
>> >>
>> >>           I think this is because the timestamps and framerate
>> >> (playout speed)
>> >>           don't match the data throughput of the MPEG stream anymore.
>> >>           (It is getting the stream too fast)
>> >>
>> >>           I put my resampled RF file at:
>> >>
>> >> http://www.olifantasia.com/projects/gnuradio/mdvh/OTA/DVB-T/ofdm_40_bw8M
>> >>hz_s amplerate_8Msps_cshort.raw
>> >>
>> >>           format is complex signed short integers (I 16 bit, Q 16 bit)
>> >> at 8
>> >>           Msamples/sec.
>> >>
>> >>
>> >>           Greetings,
>> >>           Martin
>> >>
>> >>           > > more details will follow as soon as I find some time...
>> >>           >
>> >>           > Thanks and success with your second group of tests.
>> >>           >
>> >>           > Martin
>> >>           >
>> >>           > > best regards and greetings
>> >>           > > to all fellow GNURadioers
>> >>           > >
>> >>           > > vincenzo
>> >>           > >
>> >>           > > PS
>> >>           > > Rafael, just have a look back a this thread and you'll
>> >>
>> >> find all the
>> >>
>> >>           > > info you need to do your test broadcast. Thanks for your
>> >>
>> >> interest
>> >>
>> >>           > > 2008/10/31 Martin Dudok van Heel
>> >>
>> >> <address@hidden>
>> >>
>> >>           > >         Hi Vincenzo.
>> >>           > >         How are things going with your exams.
>> >>           > >
>> >>           > >         I hope well.
>> >>           > >
>> >>           > >         Thanks for your help so far.
>> >>           > >
>> >>           > >         I finally got your DVB-T dump streams working.
>> >>           > >         I first tried using an undersampled basicTX but
>> >>
>> >> never got it
>> >>
>> >>           > >         to work.
>> >>           > >         (use a niquist mirror in the VHF range on
>> >>
>> >> channel 11 or 12
>> >>
>> >>           > >         (219.5 Mhz or 226.5 Mhz))
>> >>           > >
>> >>           > >         I now use a RFX900 and that works with a
>> >>
>> >> pinnacle PCTV-Solo
>> >>
>> >>           > >         72e usb DVB-T receiver card plugged into my PC.
>> >>           > >         I use 858.0 Mhz (channel 69)
>> >>           > >         I used a 10 dB attenuator on the antenna output
>> >>
>> >> to limit
>> >>
>> >>           > >         output power.
>> >>           > >         I also modified the RFX900 to enable
>> >>
>> >> transmitting outside of
>> >>
>> >>           > >         the ISM band. (disable saw-filter. add 220 pF
>> >>
>> >> capacitor)
>> >>
>> >>           > >         Apparantly the pinnacle 72e can receive 7 Mhz
>> >>
>> >> channels on the
>> >>
>> >>           > >         UHF channels.
>> >>           > >         My standalone settopbox DVB-T receiver can't
>> >>
>> >> handle it.
>> >>
>> >>           > >         I noticed you don't use the full possible range
>> >>
>> >> in your 16 bit
>> >>
>> >>           > >         streams.
>> >>           > >         (only goes from -80 to +80 while you could use
>> >>
>> >> -8192 to 8192)
>> >>
>> >>           > >         Is this on purpose?
>> >>           > >         I can multiply samples by 64 and get a cleaner
>> >>
>> >> signal. (But
>> >>
>> >>           > >         also more output power)
>> >>           > >
>> >>           > >
>> >>           > >         I do have a request, I hope it is not too much
>> >>
>> >> work.
>> >>
>> >>           > >         Could you make a stream with 10 Msamples/sec
>> >>
>> >> samplerate and 8
>> >>
>> >>           > >         Mhz wide channel.
>> >>           > >         This way I can use standard standalone DVB-T
>> >>
>> >> receivers and
>> >>
>> >>           > >         don't have the 7Mhz bandwith on UHF problem.
>> >>           > >
>> >>           > >         For the 10 Msps stream I would have to use my
>> >>
>> >> USRP2 to output
>> >>
>> >>           > >         it.
>> >>           > >         It has a 100 Mhz DAC (in stead of 64 Msps in the
>> >>
>> >> USRP1)
>> >>
>> >>           > >         It has a gbit ethernet connection for the
>> >>
>> >> samples, so I can go
>> >>
>> >>           > >         up to 25 Msps.
>> >>           > >         It can only do fixed interpolation rates so I
>> >>
>> >> have to choose
>> >>
>> >>           > >         from the table below.
>> >>           > >         (8 Msamples/sec is not supported on the USRP2)
>> >>           > >
>> >>           > >
>> >>           > >         USRP2
>> >>           > >         dac_rate        interp  ethernet_sample_rate
>> >>           > >         100             4       25
>> >>           > >         100             5       20
>> >>           > >         100             6       16.67
>> >>           > >         100             7       14.29
>> >>           > >         100             8       12.5
>> >>           > >         100             9       11.11
>> >>           > >         100             10      10      <----I think 10
>> >>
>> >> Msamples/sec
>> >>
>> >>           > >         should be optimal
>> >>           > >         100             11      9.09
>> >>           > >         100             12      8.33
>> >>           > >         100             13      7.69
>> >>           > >         100             14      7.14
>> >>           > >
>> >>           > >
>> >>           > >         I think 10 Msamples/sec would be a good
>> >>
>> >> candidate.
>> >>
>> >>           > >         Have you also tried using 8 Msamples/sec on the
>> >>
>> >> USRP1?
>> >>
>> >>           > >         I know there would be no room left for IF
>> >>
>> >> channel filtering,
>> >>
>> >>           > >         but it could in theory still work.
>> >>           > >         If this works I would also very much appreciate
>> >>
>> >> a 8Mhz
>> >>
>> >>           > >         bandwidth stream with 8 MSPS samplerate so I can
>> >>
>> >> demonstrate
>> >>
>> >>           > >         with a standard USRP1.
>> >>           > >
>> >>           > >         Thanks for your help so far.
>> >>           > >         I appreciate it very much.
>> >>           > >
>> >>           > >         And good luck with your exams.
>> >>           > >
>> >>           > >         Have a nice weekend.
>> >>           > >
>> >>           > >         Greetings,
>> >>           > >         Martin
>
>
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-- 
Vincenzo Pellegrini