On Fri, 2010-01-01 at 23:07 +1100, Matthew Smith wrote: > Hi all, > > I hope this is the right place to try and troubleshoot my DVB setup. I > have a Conexant based tuner that used to work with the cx88 driver and > an Avermedia USB tuner. I have moved house and can't get either of > these cards to tune using the scan or dvbscan utilities. > > Mythtv is able to pick up the channels when it scans but it can't tune > to them later when I try to watch live tv. As it tunes, I briefly see > mythtv reporting signal strengths around 40% You can use femon to see if you even get a lock on the channels. > My TV is using the same antenna (with a splitter) and it picks up the > channels and reports 30-33% signal strength and 100% signal quality. > > Also, I'm not sure I have the right channel file as I live in country > Victoria and the closest city is Melbourne so I'm using that file. I > would expect to at least tune the major channels. > > Is this just a case of needing a better antenna or is there something > else I can try? (I am already using a signal amplifier at the wall > socket.) An amplifier at the wall socket is suboptimal. For weak OTA signals, you want a low noise figure ( < 3 dB ) pre-amplifier located as close to the antenna as possible - before the splitters, long cable runs, and wall plates - so you can maintain as much of your received SNR as possible. (In the US Winegard make some good units.) Also be aware that over-amplification can overdrive the tuner front ends causing intermodulation products that show up as noise and degrade the SNR. You may find the information here useful: http://ivtvdriver.org/index.php/Howto:Improve_signal_quality once ivtvdriver.org comes back up. It seems to be down right now. Regards, Andy > Regards > > Matt > > $ scan /usr/share/dvb/dvb-t/au-Melbourne > scanning /usr/share/dvb/dvb-t/au-Melbourne > using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0' > initial transponder 226500000 1 3 9 3 1 1 0 > initial transponder 177500000 1 3 9 3 1 1 0 > initial transponder 191625000 1 3 9 3 1 1 0 > initial transponder 219500000 1 3 9 3 1 1 0 > initial transponder 536625000 1 2 9 3 1 2 0 > >>> tune to: 226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE > WARNING: >>> tuning failed!!! > >>> tune to: 226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE (tuning failed) > WARNING: >>> tuning failed!!! > >>> tune to: 177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE > WARNING: >>> tuning failed!!! > >>> tune to: 177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE (tuning failed) > WARNING: >>> tuning failed!!! > >>> tune to: 191625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE > WARNING: >>> tuning failed!!! > >>> tune to: 191625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE (tuning failed) > WARNING: >>> tuning failed!!! > >>> tune to: 219500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE > WARNING: >>> tuning failed!!! > >>> tune to: 219500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE (tuning failed) > WARNING: >>> tuning failed!!! > >>> tune to: 536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE > WARNING: >>> tuning failed!!! > >>> tune to: 536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE (tuning failed) > WARNING: >>> tuning failed!!! > ERROR: initial tuning failed > dumping lists (0 services) > Done. > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
