[mythtv-users] PVR-150 Tuner Quality Issues

Brian Wood beww at beww.org
Mon Apr 17 13:06:03 UTC 2006


On Apr 17, 2006, at 6:46 AM, Steven Adeff wrote:

> On 4/16/06, Michael Horn <mjhorn at gmail.com> wrote:
>>  Thanks everyone for the input so far. I've made some progress  
>> with the
>> picture quality, through a combination of fine tuning the  
>> frequencies as
>> well as adjusting some of the brightness,contrast etc settings on  
>> the card.
>> Ive been adjusting the brightness and whatnot using ivtvctl -y
>> brightness=xxx, but it seems that this is reset by mythtv each  
>> time the
>> channel is changed. are there global or possibly per channel  
>> settings within
>> myth I should be using instead?
>
>
>
> You can also buy a grounding block for your cable (few $$ at Radio
> Shack or Home Depot). Or just buy a Home Theatre surge supressor that
> has a cable/sat/ant passthrough which will ground and sometimes filter
> for noise your cable/sat/antenna. If your using a UPS for your Myth
> computer DON'T combine it with a surge supressor! But you can use one
> for other equipment in your home theatre and run the cable/sat/ant
> through it,


I've found that the ground potential of your AC power wiring and that  
of your TV cable are almost never the same. In my case they are  
almost 2 volts different at my computer location, and this makes  
sense because both services are probably using different ground  
references, and the resistance of the grounding conductors will  
differ due to different distances, types of conductors etc.

Add to this some devices that ground at multiple points, USB capture  
devices have "ground" at the RF connector shield, the USB connector  
and (possibly) the DC power supply, all of which are just about  
guaranteed to be different.

The best bet is to tie all of these together at close to the computer  
as possible, but grounding can be a tricky thing, an sometimes  
lifting grounds from things and allowing them to float can actually  
improve things.

In any case, if you play around with grounding, top priority should  
be given to the "safety" ground of the PC case (as opposed to the  
"neutral" of the AC power system, or the various signal grounds). You  
really do not want to wind up with a case that's "hot" with respect  
to earth ground, which could cause things like your family collecting  
on your insurance policy.



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