Hi Vincenzo, On Sun, 2008-11-02 at 01:28 +0100, Vincenzo Pellegrini wrote: > Hi Martin, > sorry for the delayed replies but now I've passed my first cluster of > PhD tests (went well)
Congratulations. > and I've got to carry out some work + preparing the second group of > tests. Success. > Well, really glad to know that you managed to receive my signals. > Yup dvb-t sticks can actually receive 7 MHz channels everywhere, I found that some of them need special "australian 7MHz at UHF" firmware to get this to work. Luckily my DVB-T usb stick doesn't need this trick. > Well, actually any DVB-T chipset can but typically manufacturers > impose strange limitations on set-top-boxes such as "7 MHz chanels > accepted only in VHF" I don't really know why. > > The signal I provided you with is suitable for both 7 and 8 MHz > channels without any modification needed. The only thing you have to > do is to set your sampling frequency a bit higher. this should be > possible with USRP2. The receiver might still have a problem that it is getting in the MPEG streams at a higher rate then realtime. > 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. > 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
