Hi Ihab, Those "restart aquisition" are generated by the ofdm_sym_acquisition block when it does not find a peak on the correlation function he uses to detect the beginning of the OFDM symbol. You should verify there is indeed a DVB signal precisely at 570 MHz. To do this you may use our "Sym Align OFDM" block (not a very nice name) available with gr-isdbt ( https://github.com/git-artes/gr-isdbt) and check that you see a "triangle" (please refer to the readme, the examples, and even the issues on our git). The symbol alignment is totally equivalent between DVB-T and ISDB-T. Moreover, I see several "O"s, meaning that somewhere samples are being dropped. That does not help either. If you do not have a very fast machine, you may use at the beginning of the flowgraph a "Stream to Vector" followed by a "Vector to Stream" with a very big "Num Items" (some millions). best Federico
2015-11-26 12:59 GMT-03:00 Ihab Zine <ihab.zin...@gmail.com>: > Hi, > > I’m trying to receive a live signal from an antenna on the roof through a > cable connected to my SDR (hackrf one ).The bandwidth of the DVB-T in > ireland is 8 Mhz , and the parametetrs Here in ireland as following: > > Bandwidth: 8 MHz > Stream code rate (hi prio): FEC 2/3 > Stream code rate (lo prio): FEC 2/3 > Modulation: QAM 64 > Transmission mode: 8k mode > Guard interval: 1/32 > Hierarchy: none > > net_data_rate = 24.128 Mbits/s > > I used dvbt_rx_demo_8k_QAM64_rate78.grc flow graph with the following > changes : > > - > > frequency of hackrf one = 570 Mhz, sampling rate = ((8*8e6)/7). > - > > Cyclic Prefix to (8192/32, is this right?) > - > > Code Rate HP : 2/3 > - > > Code Rate LP : 2/3 > - > > Guard Interval : 1/32 > > The problem i have is that no output data coming out after the > demod_reference_signals BLOCK(no cancellation map), and got the following: > > restart aquisition > > OOrestart aquisition > > d_freq_offset: -5 > > Od_freq_offset: -5 > > d_freq_offset: -5 > > d_freq_offset: -5 > > d_freq_offset: -5 > > d_freq_offset: -5 > > d_freq_offset: -5 > > d_freq_offset: -5 > > restart aquisition > > OOd_freq_offset: -5 > > d_freq_offset: -5 > > > > so I had to add a signal source to shift the signal. After shfting the > signal i got the following : > > restart aquisition > > restart aquisition > > restart aquisition > > restart aquisition > > Orestart aquisition > > > > I have read a lot about DVB , mapping ,ofdm and others, i have spent weeks > on this but still the same problem, if it is synchronization problem what i > should do? > > So please i need a some help with this problem . > > > > Thanks > > Ihab > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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