What sort of testing meter do I need?

catherinetApril 23, 2010

I'm still struggling with severe TV interference on hot afternoons. The TV guy is barking up the wrong tree, by replacing the antenna. Now he wants to do more testing but I don't trust him.

What device is needed to see if some outlet is mis-wired?

Also....how would I test for a defective door bell and/or door bell transformer. I'm thinking these are things we can do on our own.


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I would try turning off the breakers one at a time while an assistant observes the interference and lets you know if it is affected. Then turn off everything but the tv circuit and see if it clears up. You may have to change the circuit that the tv is plugged into via moving it or an extension cord to see if the tv circuit is the cause. By turnining off your door bell circuit you will have confirmed or eliminated it. If you locate the circuit or circuits that cause the interference you are on your way toward fixing the problem.

    Bookmark   April 23, 2010 at 11:45AM
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How do I turn off things that are hardwired into the circuit? There are many things on this one circuit, including the doorbell. They can't all be unplugged. How do I disconnect them?

    Bookmark   April 23, 2010 at 1:25PM
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To disconnect items like your doorbell, turn off the circuit breaker, or remove the fuse for that circuit.

It is highly unlikely that a device like a door bell buzzer would cause TV interference. Does it only happen when someone rings the bell?

The most likely cause of periodic TV interference is from device emitting RF (radio frequency) waves (through the air). Common causes are things like ham radio operators, cell towers, airport control towers, etc. Bad connections to your antenna could also be a cause, so don't be too quick to discount your repairman.

    Bookmark   April 23, 2010 at 2:45PM
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In troubleshooting we rarely start at the finish line. You may never need to know how to disconnect anything,
just as with your meter question, the equipment you asked about would certainly be very expensive and well out of any homeowners price range, especially one that is here asking how to do it themself, but you probably don't need it. You will however have to start at the beginning and do the simple things first. Have you found the circuit responsible for the interference?

    Bookmark   April 23, 2010 at 3:51PM
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I just read your other thread. Why did you need to start a new one for the same problem? It seems that you do know what circuit is causing the problem and it very well may be the bell transformer that is the cause. How many things, besides the transformer, are there on this circuit that can not be turned off. To unhook the transformer, turn off breaker and unhook the wires to it, being careful to replace the wirenuts on the power supply wires. You can then turn the circuit back on. You may experience a new strange knocking sound from the front door area.

    Bookmark   April 23, 2010 at 6:39PM
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I started a new one because sometimes when a thread has been there awhile, no one looks at it anymore.
I guess the testing meter is too expensive, so we'll figure something else out.

    Bookmark   April 23, 2010 at 7:26PM
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You haven't said what all it is thats on this circuit, or if you have tried it with the transformer disconnected. If you have tried disconnecting the transformer and still have a problem, I have the meter for you. It is an portable AM radio tuned off of any station with the volume turned up. It ain't sexy but it should work. Move it along the circuit from electrical panel to the end of the circuit and it should make more noise than a dope dealers cell phone on Saturday night.

    Bookmark   April 23, 2010 at 10:39PM
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A good piece of test equipment for finding rf interference would be a small transistor radio tuned to the higher end of the scale, say around 1090. Move the tuner slightly off any broadcasts. As you get closer to the source of interference, the you will hear it in the radio. The interference will increase as you get closer to the cause. Grounrod gave good instructions on how to disconnect items from the circuit that are hard wired.

You didn't give any description of the characteristics of the interference you are getting. If you are getting what appears to be dotted and dashed lines running diagonally or horizontally across the screen during warmer temperature changes, your problem gives all indications it is in the antenna cable itself. I think you might want to (or have someone) check any and all of the cable connections from the antenna to the tv. The crimped connections can go bad, the screw on type are apt to cause problems. If the cable has any of the bullet type screw on adapters for splices, they can become corroded over time or loose. Tighten them as well as the connection on the tv. As you go along checking the connections, have someone observe the tv. When you hit the bad one, it'll be evident. Just an fyi....if the antenna wasn't damaged, it didn't need to be replaced.

Check it out and please get back to us.

    Bookmark   April 23, 2010 at 10:41PM
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Hey maryland
great minds think alike.
where do you procure your interference meters from?

    Bookmark   April 23, 2010 at 10:59PM
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Any of the wholesale supply houses that provide electrical and testing supplies have them or, can get them. I bought my last (and most accurate) meter from a Security Supply Company. It is used to scan for electronic bugs. I'm a glutton for test equipment and this one does great. It's pretty sensitive and can narrow you right down to the spot. I was in Harbor Freight and I saw one of their versions for sale too. I'll pick one up one day and play with it, they're cheap.

    Bookmark   April 23, 2010 at 11:56PM
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Borrow a battery powered TV and then turn off the
main breaker and check the reception.

    Bookmark   April 24, 2010 at 9:12AM
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I've got some battery TV's that I will sell you, but they are analog.

    Bookmark   April 24, 2010 at 10:31AM
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