DVB-T Interferences (1 Viewer)

miljbee

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November 11, 2005
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Hi all,

not sure this is the right place to put this post, so dear moderators, feel free to move this post wherever you want.

I am experiencing problems to receive DVB-T Signal correctly. A Lot of frames are dropped.

Before i set up my htpc i have tryed my Hauppauge HVR 1300 on my other computer and it worked just fine. Picture quality was good, there wasn't any problems with picture quality.

In the HTPC, i think that one componnent generates interference that avoid DVB-T Signal to be received correctly.
When i put my hand over the CPU (without touching it of course) the TV quality is immediately greatly improved. I think that my hand is a sort of shield that catches interferences .... So i have replaced the cpu fan. The problem is still the same. I have also tried another PSU, still the same problem. I don't think this is the graphic board since i have tried another one with the same result. The remaing parts to test are the hard drive, the mother board, and the case. Of course, i will try to test them, but i was wondering if someone here have already experienced such a problem and how it has been fixed.

Do you think it could work better with an external (USB) TV Board ?
is there some sorts of electronics that coud catch interferences (like my hand !) ?

A last thing : the case of the HTPC is a self made one. It is wood. The first computer in whitch i have surccesfully tested the board has a steel case ...

Thanks for your advices.
 

jawbroken

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August 13, 2005
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You may have an issue with intererence because of the wooden case. I know that in a regular steel case the entire case is grounded in order to reduce EMI. I am not sure though.
 

jawbroken

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Electromagnetic interference. For example, an over-the-air DVB signal is an electromagnetic signal. A Radio signal is also electromagnetic.

I don't know if this is your problem, though.
 

jawbroken

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I believe that the case is connected to the motherboard ground. Which will be the same as ground on the molex connectors from the PSU.
 

miljbee

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November 11, 2005
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Orléans, France
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i have just had another idea :

I know that in cars there is a sort of module that reduce interferences. If this piece of electronic is not present, it isn't possible to get radio. Now all cars are equiped with it but a long time ago it wasn't the case.

Would this piece of electronic help me with my problem ?
 

Marcusb

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  • February 16, 2005
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    you're thinking of a condensor, which is basically a capacitor or inductor wrapped around the inout lead. Don't think it would help here as all the cicuit boards are exposed to each other. In a car your stereo is surrounded by a steel case, which is also grounded.

    In most bioses you have the option to turn on spread spectrum control.
    You lose a *tiny* bit of performance, but the motherboard does a *lot* of effort to reduce EMI as much as possible. Experiemtn with different settings of this.

    If that fails, get a piece of copper or something similar, ground it to the posersupply with a wire and mount it on the back of the TV card (Make VERY sure that you insulate anything so it can't short anything out).

    If both of these fail then try a USB unit instead. It should be much better, but since you have a wooden case then it may still get EMI.
     

    Taipan

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  • February 23, 2005
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    miljbee said:
    Would this piece of electronic help me with my problem ?
    I very much doubt that it would - the item you are referring to is resistive spark plug leads and capacitors on the spark coil.

    I believe that your problem is caused by the wood case - it needs to be a metal case to effectively ground all the EMI that is generated within your PC.

    If you want to retain the wood PC case, then you need to line the inside of the case with an electrically conductive coating - aluminium foil, for example, or a spray-on coating (paint) that is very conductive. Dell, for example, do this on the inside of their plastic PC cases. This conductive surface needs to be electrically connected to the PC ground to be effective.

    BUT, before you go to all that trouble (to line the wood case with a conductive surface), I suggest you move the motherboard and all the other items into a standard metal PC case to prove that this will solve the problem.
     

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