[mythtv-users] Low signal problem

Jan Schneider jan at horde.org
Tue Jan 27 00:06:54 UTC 2009


Hi,

I have some problems with my signal level and quality, and I'm running  
out of ideas.

I have freshly built, nicely equipped combined backend/frontend:
SilverStone LC16M
SilverStone 300W fanless PSU
Asus M3V78 PRO with on-board GeForce 8300
Athlon 64 5050e
2GB 800MHz
TechnoTrend C-2300 (DVB-C)
One of those WD VDR/Green drives
Mythbuntu 8.10 (Kernel 2.6.27.9, MythTV 0.21.0+fixes18722-0ubuntu1)

The problem is that I can hardly tune into certain channels. I get  
tons of bit errors and buffer underruns in the backend logs. And if I  
get an image at all, it's flaky at best. Of course it varies between  
different stations.

Signal strength is usually 77%, SNR is ca. 3.8dB/15%. Typical CPU  
utilization is 40%, load is below 1. The weird thing is that the  
signal strength and quality are both 100% when using the cable box  
(also from TechnoTrend) on exactly the same connector. So most of the  
advises I could find don't apply:

- I tried adding an amplifier, but that didn't help of course, because  
it only raised values to 78% and 4dB, but it made the problem even  
worse, almost no image at all.
- It shouldn't be a problem with the cable, because the settop box  
works. I tried removing the cable completely (there is no wall socket,  
just a cable coming out of the wall that I can't replace. Don't ask.)
- The cables have a nice fit into the tv card.
- I tried different PCI slots because that's what someone suggested.
- I tried a different power plug for the HTPC machine.
- I checked the ground connection. Antenna ground to power ground has  
a resistance of 250 Ohm, no idea if that is a good or bad value.

*Any* further ideas are highly appreciated.

Thanks, Jan.

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