Comp causes OTA reception issues??

[impala454]

So I am messing around with my second computer, which is currently sitting about 3 ft away from my DLP TV, and about 4-5 ft away from my terk HDTV antenna. I'm sitting here watching football while working on the PC, and noticed that my reception was really getting bad, to the point that I no longer got a picture at all. I then realized that upon turning off the PC, the reception instantly came back, perfect HD and everything... granted I do have the actual PC open while I'm working on it, so I wonder if there is really that much EMI coming out of the comp? Or if it is simply a matter of power or something (although the PC is plugged into a different outlet than the TV and antenna). Anyone else seen anything like this?

[madmac]

Well, If turning off the computer solves the bad reception issue, then you have found the cause for sure!. The computer is either affecting the TV or the HDTV antenna or both for that matter. You could try plugging the computer into a different receptacle and see if that helps?. Worse case, you'll have to move the computer away from the TV.

[JeremyG]

Huh, pretty weird Chuck. Do you have a power supply or something that's not grounded? Did you check a bunch of TV channels to see if they all had problems? We use a big OTA antenna in the attic, and when certain appliances kick on they momentarily scramble TV reception on all channels. Could be EMI, could be on the electrical lines. But that is only for a second or two. I'm interested to hear what you find out.

[impala454]

I confirmed it does affect all channels. It's an indefinite effect, as in it keeps interrupting the channel until I shut the PC off. Also to clarify, the devices are all plugged into the same circuit. My curiosity is whether it's an EMI issue or power. If it's EMI then maybe it'd be possible to build a pseudo faraday cage around the inside of the PC case or something.

This is almost perfect timing though as our payload at work is going in for EMI testing so maybe I can quiz the guys there.

[JeremyG]

We have a dedicated group that works EMI. Usually when we find a problem and it's not a component defect they'll either install a power filter in line with the offending unit, or add a ground. Sounds to me like you have a ground issue or a bad power supply. Why don't you try wrapping it with aluminum foil and see if it helps? Sounds funny, but it could. Just don't overheat anything.

[JeremyG]

You might also have something shorted together acting like an antenna, thus amplifying the effects.

I hate these kind of things. I had a problem in my living room earlier this year where whenever I was listening to the HT, and turned the overhead fan light on, the left and right mains would pop. It ended up being that the power supply in the fan would cause the issue only if the fan motor was on while I turned the light kit on. The light kit by itself wouldn't cause the issue. Since I couldn't change the fan out (well, the wife said no) I tracked the other side of the issue to a cheap pair of RCA's what went from my AVR to my UPA-2. I built a new set of cables with good connectors and coax, and no more problem.

[madmac]

Just an FYI about OTA DTV reception. DTV over the air is vastly better than the old analog broadcasts. They travel farther and of course, produce a stunning, widescreen 1080i picture with dolby digital sound thrown in for good measure!.

They can be finicky though!. Stuff like the computer mentioned above, airplanes flying overhead, bad weather etc. can reek havoc on the DTV signal causing blackouts or not getting the reception you had yesterday no problem at all the next day!. I wanted to watch golf yesterday afternoon but my NBC signal was too dodgy and there were too many blackouts so I just walked away. DTV is either on, or it's off. Unlike the analog signals where you would get 'snow' if the signal was not great, Your TV picture and sound will simply shut off if the signal is compromised.......some days, it's just gone altogether, probably due to some weather disruptions somewhere between your antenna, and the broadcast one.

All that being said though, 99% of the time I get a crystal clear picture and sound no problem. I have a small outdoor antenna with a rotor incorporated to fine tune the signal if needed. Remember one thing, the bigger the antenna, the better DTV signal you'll get with fewer blackouts. Another thing is the location of the antenna. That is paramount to good DTV playback. Even the movement of a few inches can make a huge difference in the consistency of the signal. Remember, free is as free does so what your getting for free here is absolutely fabulous compared to what used to be!!.

[Kevin P]

Have you tried putting the cover on the PC? The cover does work to keep RFI/EMI from escaping from the PC innards and interfering with things like OTA TV reception. That's why plastic cases have a metal shield on the cover. Also check to make sure the case is grounded.

[impala454]

Yes I did actually close the PC case once I was done piddling with it, and the signal improved but was still horrible. I think Jeremy could be right in that it might be the PC's power supply, as it has been acting up. I moved it to another room altogether for now, just thought it was pretty crazy how it was night and day. PC on, boom, OTA signal 100% gone, PC off, OTA signal 100% crystal clear. I'll have to keep playing with it. Might start building PCs with little faraday cage like liners or something (new snake oil business? anyone? :P)

[JeremyG]

I talked to one of our EMI guys today. He seconded the power supply.

[impala454]

Hmm I might actually pull the PS out of the case and run it standalone to test that theory. That is one part I have had horrible luck with in computers over the years. Didn't matter whether I bought a top of the line PS or a POS PS (heh). Almost always the first component to fail for me.

[Hdale85]

Well PSU's are one of the most stressed components generally. I've never had much issue with a decent quality unit. Generally I always buy something in the gold certified area.