[mythtv-users] Interference lines in all recordings
Tim Gray
tim at p-a-a-i.com
Mon Feb 12 13:44:29 UTC 2007
I was silly and built a nice tiny setup. 2 pci slots only and it's a
micro itx with everything built on board as it's a backend recorder
only. I have not tried the move the wores around although at the start I
tye wraped all wires away from the cards as far as I could go assuming
that anything inside the case will mess with the cards to begin with. I
will try soldering down the can caps, I am sure it will help if it does
not fix the problem. I also never thought of the over/underclocking
thing. I'll give that a try and see what happens with the recordings.
I was also thinking of cutting a piece of aluminum and grounding it, and
wrap it in electrical tape and slide it in-between the two cards just in
case they are interfering with each other.
the 3 motherboard screws are tight, the rest are those teflon standoffs.
Thanks a ton for your help and ideas, I'll see what happens with all
these different suggestions and report back.
Brian Wood wrote:
> 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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