TV tunes ok but my DVB cards won't tune

TV tunes ok but my DVB cards won't tune

[Matthew Smith]

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%

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.)

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.

Re: TV tunes ok but my DVB cards won't tune

[Andy Walls]

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.
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