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_bw8Mhz_samplerate_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 <[EMAIL PROTECTED]> > > 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 > > > > > > > > > > -- > > Vincenzo Pellegrini _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
