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I've recently changed my computer case to a new, bigger case. However, after I changed this case over, I can no longer watch TV due to interference with the signal.

I have removed every output to my computer (e.g. internet, visual, sound etc) which has not changed the affect at all. I have bout a new PSU which did not change the problem.

The aerial is in the loft above my PC but, this was not an issue before I changed my case.

I noticed a change in the interference when I removed my water cooler and replaced it with a stock CPU cooler. The interference then "moved" from the originally affected channels to some lesser used channels.

Could anyone suggest what is causing this interference?

Thanks

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What is a CPU cleaner? :-) –  Anindo Ghosh Nov 26 '12 at 16:32
    
I have no idea :) CPU Cooler is what I meant, thanks. –  Pixedo Nov 26 '12 at 16:41
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2 Answers

It sounds like your new case has a lot less metal than the old case, and is allowing signals from the CPU (and the motherboard in general) out. The CPU heatsink is closely coupled to the CPU chip, and acts as an antenna for those signals. Undoubtedly, the electrically-conductive parts of the conventional (air-based) cooler have different resonant frequencies than those of the water-based cooler, and this would explain the shift in frequency of the interference you're experiencing.

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Well, in fact, it's probably the other way around. My new case is a big NZXT Phantom which is completely metal, and about 2-3 times the size of my old case which was a small, cheap case. Is there a reason that this would affect the signals more than in the old case? –  Pixedo Nov 26 '12 at 16:49
    
In that case, perhaps the new case has some panels that are not well-connected to each other, creating one or more slot antennas. Verify that each separate piece of metal in the new case is solidly connected (in the electrcial sense) to its neighbors, along the full length of each joint. Look for missing welds, screws or spring fingers/gaskets. –  Dave Tweed Nov 26 '12 at 18:39
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Quite possibly, the old computer case was grounded and the new one isn't.

Faraday cages do a good job at keeping electric fields out.

But to keep electric fields in, they have to be grounded.

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This makes sense and was the original conclusion I came to. After searching another forum, I came to the conclusion that missing out the rubber washers on my motherboard was causing some interference. I placed in some new washers (not rubber) which made a noticeable difference in the interference. The issue is, I don't know how to ground my case, or test if it is grounded. –  Pixedo Nov 26 '12 at 16:52
    
Use your multimeter to check for continuity between the case and the ground (third prong of the power supply). With the unit unplugged, needless to say. –  Kaz Nov 26 '12 at 17:05
    
I think computer power supplies do not usually have a ground wire. They ground to their own case. An external ground wire should be installed from the power supply to the computer case, instead of relying on the contact between the cases. If your power supply does have a ground wire (perhaps a green wire with a screw-hole terminal on the end), attach that to the case. –  Kaz Nov 26 '12 at 17:23
    
There are many good reasons to make sure the case is grounded, but it will actually have very little, if any, effect on its ability to contain (or radiate) interference in the VHF/UHF spectrum. –  Dave Tweed Nov 26 '12 at 18:52
    
Thanks, Ill try to dig out a multi meter when I'm home and see what I can achieve. I know that my power supply does not have a ground cable as I'm pretty sure that all cases ground through touching the PSU. Apart from this, I have no idea what would cause this issue. –  Pixedo Nov 27 '12 at 10:57
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