[mythtv-users] Interference lines in all recordings

Brian Wood beww at beww.org
Fri Feb 9 20:30:46 UTC 2007

On Feb 9, 2007, at 1:14 PM, Tim Gray wrote:

> Thanks a bunch, I already ran that route...
> Cables are hand made RG6quad with firmly crimped connectors, they are
> good.  they go into a single splitter to take the signal into both  
> cards
> whuch works good when you view from a TV on the same.  I also have  
> +10DB
> CATV signal coming in as far as my NTSC/QUAM cable analyzer is telling
> me, although channel 96 is only +3DB so there is a little bit of
> difference from one end to the other.
> signal coming into the tuners is verified to be 100% interference free
> by hooking up a replayTV and viewing recordings that are 100% clear.
> which leads me to be sure the interference is coming from inside  
> the PC.
> Has anyone found a way to shield the cards better or ground them  
> better
> to get rid of PC generated interference?

Great, it sounds like you know what you're doing, but I had no way to  
know that at first :-)

I assume you've tried moving your PVRs to different slots, if you  
have them. I'm guessing you're getting interference with the baseband  
video on the PVRs and not RF into the tuners, but it couldn't hurt to  
make sure the can tops are tight, or even solder them.

What sort of PC is this? Could you re-route internal cables to try  
and get them away from the PVRs?

Otherwise you are talking about trying to put shielding material  
around the cards, not any fun but it might be your only solution.

Also make sure all the motherboard mounting screws are tight, loose  
connections can act as detectors and cause trouble.

If there are any cards in the PC that you can get rid of do that as  
well, but I suspect you've tried that if it's even posible.

If there's any way you can narrow things down to what portion of the  
PC is generating the interference it would help. For example if you  
could boot without a graphics card and SSH into the machine to make a  
manual recording you could prove or eliminate that card as the source  
of the problem.

This one's a little off the wall: If you can change the frequency of  
the interference you might cause the beats to be moving fast enough  
to at least be less disturbing. Under/Over clocking the machine by  
5%-10% might cause a significant change in the perceived if not the  
measured interference.

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