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  #1  
Old 05-02-2012, 09:55 PM
KellyCriterion KellyCriterion is offline
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What is causing interference to my digital TV signal?

Hello,

I have a digital TV (Panasonic Viera), the antenna cable is plugged in to the wall (connected to the antenna on the roof).

The reception is great most of the time, except when:

The bathroom light is switched on. When this light is on, the reception suffers extreme interference, (extreme pixelization, heavily interrupted sound, etc). The interference remains as long as the light is switched on. When we switch it off, the TV picture and sound quality restores immediately.

We also get a similar effect when we hold down the "recline" buttons on our electric recliners.

When we are watching a DVD or using the PlayStation, the TV is unaffected by light switching or reclining.

What is the likely problem here? Thanks.
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  #2  
Old 05-02-2012, 10:19 PM
Michael63129 Michael63129 is offline
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My first thought is noise on the power line; this is especially likely if the bathroom light is a CFL or LED; the recliner similarly can produce noise from its motor. You could try a line filter on the TV and/or recliners and if you have one, put an incandescent in the bathroom light and see if the problem goes away (if it already is an incandescent, then that makes this a problem that I don't know the answer to, since incandescent bulbs can't cause interference unless a dimmer is used). Most likely, the same circuit supplies power to the TV and the offending devices. Note however that noise can also be radiated through the air and a line filter won't help in this case (but then other CFL/LED lights should cause interference, but they might be a different/better brand).
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  #3  
Old 05-02-2012, 10:56 PM
johnpost johnpost is offline
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dimmers and electric controls (like in chair) can generate electric noise both into the wiring and into the air, this interferes with your tv signal.
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  #4  
Old 05-02-2012, 11:34 PM
KellyCriterion KellyCriterion is offline
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Quote:
Originally Posted by Michael63129 View Post
My first thought is noise on the power line; this is especially likely if the bathroom light is a CFL or LED; the recliner similarly can produce noise from its motor. You could try a line filter on the TV and/or recliners and if you have one, put an incandescent in the bathroom light and see if the problem goes away (if it already is an incandescent, then that makes this a problem that I don't know the answer to, since incandescent bulbs can't cause interference unless a dimmer is used). Most likely, the same circuit supplies power to the TV and the offending devices. Note however that noise can also be radiated through the air and a line filter won't help in this case (but then other CFL/LED lights should cause interference, but they might be a different/better brand).
Thanks for the tips, your mention about 'sound' reminded me that sometimes we can resolve the interference by pressing mute on the TV remote. Does that offer any more clues?

I am not sure what kind of light is in the bathroom as I haven't had to change the bulb yet, and I guess I just don't look up (I only moved in to this house a short time ago). My hunch is that it would be a standard bayonet cap lightbulb, because pretty much every other bulb in the house is.
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  #5  
Old 05-02-2012, 11:52 PM
Joey P Joey P is offline
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I'm going to guess that if you can gain access to the wiring, the cable/antenna runs very close to electrical wiring to the bathroom. If you can spread them out it might alleviate the issue.
A quick way to check this out would be to run a cable from the TV to the antenna directly. That is, connect one end to the TV, then send the cable out the window and up to the roof or attic or wherever it connects. This way it stays away from any electrical wiring. If you no longer have the problem, then this is probably the case and you'll need to either physically separate the wires or if that's not possible abandon the old one and run a new one in a different route.

FTR, my first thought when I saw that lights were involved was that they were probably florescent. Check them out. If they're CFLs, try replacing them with regular bulbs. That would be the easiest solution.

Also, are there other TVs in the house? Do they have problems?

Last edited by Joey P; 05-02-2012 at 11:54 PM..
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  #6  
Old 05-03-2012, 12:28 AM
KellyCriterion KellyCriterion is offline
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Quote:
Originally Posted by Joey P View Post
I'm going to guess that if you can gain access to the wiring, the cable/antenna runs very close to electrical wiring to the bathroom. If you can spread them out it might alleviate the issue.
A quick way to check this out would be to run a cable from the TV to the antenna directly. That is, connect one end to the TV, then send the cable out the window and up to the roof or attic or wherever it connects. This way it stays away from any electrical wiring. If you no longer have the problem, then this is probably the case and you'll need to either physically separate the wires or if that's not possible abandon the old one and run a new one in a different route.

FTR, my first thought when I saw that lights were involved was that they were probably florescent. Check them out. If they're CFLs, try replacing them with regular bulbs. That would be the easiest solution.

Also, are there other TVs in the house? Do they have problems?
Thanks for your thoughts.

No other TVs in the house, no. I'll check the bathroom light when I'm next home.
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  #7  
Old 05-03-2012, 11:17 PM
al27052 al27052 is offline
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You might try wrapping the cable line to the TV in aluminum foil, specifically the part of the line in the attic. I've done that to stop electrical interference before, it works great.

Since the video feed is unaffected when using the Playstation, I really doubt there's actual noise on the power line. Try the aluminum foil. Let me know if it doesn't work.

You don't have to wrap it thickly, just pull a long sheet of it lengthwise down the cable and just sort of crush it around the cable.
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  #8  
Old 05-10-2012, 10:34 PM
KellyCriterion KellyCriterion is offline
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UPDATE:

The bathroom light is a standard incandescent lightbulb.

Using a quad shield cable to connect the TV to the antenna socket on the wall did not make any difference.

There is also an outside light (incandescent) that when it's switched on, causes a smaller amount of continuous interference for as long as it's switched on.

Sometimes muting the sound on the television can fix the interference problem(!!) (The audio is not being routed through any special stereo or speakers etc, it's just standard sound straight out of the TV).

Does it now seem most likely that the problem is the antenna cable (in the wall) is running too close to the electric circuit?

Last edited by KellyCriterion; 05-10-2012 at 10:34 PM..
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  #9  
Old 05-10-2012, 11:01 PM
Joey P Joey P is offline
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Quote:
Originally Posted by KellyCriterion View Post
Using a quad shield cable to connect the TV to the antenna socket on the wall did not make any difference.
If there's interference entering the cable the chance that it's happening in those last few feet is pretty slim, especially given what you've told us. It still sounds like it's electrical interference somewhere in the walls and I'm going to guess that at some point the cable from the TV to the antenna runs very close to an electrical cable. Very close as in, right up against each other for a few feet. Also, if your house is about 30 years old or so (or the cable is) it's probably that very thin cheap gray stuff that was installed with a lot of antenna systems with little or no shielding.

How big of a deal is it for you to get access to some of these areas? Is your house one story? Is the attic finished? If it's one story and the attic is unfinished this might be as simple as climbing up there, seeing if you can find the two wires next to each other and just physically pulling them apart as much as you can. If the house is two stories and everything is drywalled and you don't want to start punching holes...it might be a 'well, we'll just live with it' type thing.

I know you said it doesn't happen with the DVD or Playstation, but just for kicks, you might want to try running an extension cord from the TV to another outlet on another breaker...just for fun. Start with something free and easy before you spend a ton of time and money chasing dead ends. Might as well rule out the circuit and outlet if we can.
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  #10  
Old 05-11-2012, 02:00 AM
GuanoLad GuanoLad is online now
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Ghosts.

I had trouble with my digital TV reception, but it was caused by rain and a rotted cable.

My negative two cents there.
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  #11  
Old 05-11-2012, 02:02 AM
KellyCriterion KellyCriterion is offline
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Quote:
Originally Posted by Joey P View Post
I know you said it doesn't happen with the DVD or Playstation, but just for kicks, you might want to try running an extension cord from the TV to another outlet on another breaker...just for fun. Start with something free and easy before you spend a ton of time and money chasing dead ends. Might as well rule out the circuit and outlet if we can.
Good suggestion, thank you. Will report back with results.
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  #12  
Old 05-11-2012, 07:47 AM
johnpost johnpost is offline
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even if you find the cause often the remedy might be adaptive use; not using the porch light, chair movement, bathroom light during times of important tv watching. keep a flashlight near the bathroom.

antenna wires running near electrical cables can sometimes cause a problem for the antenna signal.

light dimmers, bad switches, loose fitting bulbs, motor controls can cause electrical noise that could be causing the problem.

using extension cords for long term wiring substitutions is not always the best solution. the cords are subject to damage depending on where and how used. the cord might get unplugged and you might have to do the setup process again on the tv.
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  #13  
Old 05-11-2012, 09:45 AM
Joey P Joey P is offline
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Originally Posted by johnpost View Post
using extension cords for long term wiring substitutions is not always the best solution. the cords are subject to damage depending on where and how used. the cord might get unplugged and you might have to do the setup process again on the tv.
I agree (not that you were disagreeing with me), I was just troubleshooting. On the off chance that interference disappeared if the OP ran a extension cord to, say, the kitchen then we would know that the problem isn't with interference coming in through the antenna cable but through the electrical wiring and we can focus on that.
I'm guessing this won't do anything, but since it's so easy to rule out...
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  #14  
Old 05-11-2012, 04:55 PM
phxjcc phxjcc is offline
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Assuming that you have a two prong power cord, right?

Try using a protective powerstrip with a three prong cord that plugs into the wall, then plug the TV into the powerstrip. The higher impedance of the power strip combined with the grounding prong might be able to filter this out.

If this does not do it, you will need an EMI filter to put in-line in the antenna circuit.

I suggest you call a knowledgeable Home Electronics outfit and ask them. Forget Best Buy, etc. I would call Crutchfield Electronics, they are very good and are likely to either have what you need or can point you to a vendor that has what you need.

Like this: http://www.crutchfield.com/p_6593410....html?tp=12614
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  #15  
Old 05-11-2012, 05:21 PM
johnpost johnpost is offline
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for testing purposes, if you have a strong enough signal from even one station, try a set top antenna (rabbit ears, loop or bow tie).
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  #16  
Old 05-13-2012, 08:30 PM
KellyCriterion KellyCriterion is offline
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Quick update.. running an extension cord to the farthest power socket in the house did not fix the issue.

Will address other posts when I have time - thank you for your tips. I may need to just end up calling an expert out to the house.
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  #17  
Old 05-13-2012, 08:48 PM
Joey P Joey P is offline
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Quote:
Originally Posted by KellyCriterion View Post
Quick update.. running an extension cord to the farthest power socket in the house did not fix the issue.

Will address other posts when I have time - thank you for your tips. I may need to just end up calling an expert out to the house.
Something else easy you can do that I suggested earlier is to run a cable from your TV directly to where it connects to your antenna. Whether that's out a window and up to the roof or up the stairs and into the attic. Either way, you'll be far enough away from any electrical wires that if there's no problem when you turn on the lights you can be fairly confident that the issue lies with the proximity of the two wires at some point, somewhere and it's just a matter of finding it.
If your house is only one story, running a new, higher quality, cable, thought a different stud bay really isn't that big of deal. Especially if you can borrow some fish tape from someone.

Last edited by Joey P; 05-13-2012 at 08:49 PM..
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