# Locating Source of EM Interference?



## SayWhat? (Jun 7, 2009)

I'm getting some heavy EM interference from somewhere and I can't find out what's doing it. Digital is gone completely, no lock on any channel, even the strongest one.. Analog video is heavily distorted with what looks like 60Hz lines. Analog audio is clear.

It's happened before and I've gone around the house turning off everything from fans to refrig and freezer, flourescent lights, power supplies and anything else I could think of, even the antenna pre-amp. It might last a few minutes or several hours.

When it started today, I realized that the attic power ventilator was on, so I shut it off. No change. I'm not even sure it's something inside the house, but there really isn't anything close by outside. No neighbors close by that might have high power radio equipment. No high voltage poower lines.

It comes and goes with no pattern as to time of day or day of week. It might happen two days in a row, or not for several weeks.

All analog TV channels are affected. FM radio is not affected.

Don't know what else to look for.


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## T_N_T (Sep 9, 2008)

SayWhat? said:


> I'm getting some heavy EM interference from somewhere and I can't find out what's doing it. Digital is gone completely, no lock on any channel, even the strongest one.. Analog video is heavily distorted with what looks like 60Hz lines. Analog audio is clear.
> 
> It's happened before and I've gone around the house turning off everything from fans to refrig and freezer, flourescent lights, power supplies and anything else I could think of, even the antenna pre-amp. It might last a few minutes or several hours.
> 
> ...


I don't know what it is, but I have the inverse problem. TV is fine, but FM/AM get it, on FM there is a strange sound on parts on the band(a loud noise, its like a buzzing) and some of the band the frequencies are just covered up by dead noise,meaning that it is like there is a station there but there is no voice, I can only get the big stations + in digital. On AM the stations are very distorted and getting a digital signal is very hard even on 1510 WLAC from Nashville. Three things, I live in a development where there is frequent construction, there is some sort of TV audio on 87.7(but it sounds like someone is switching the channel every now and then) and I also can pick up what sounds like running water on my scanner.


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## Tower Guy (Jul 27, 2005)

SayWhat? said:


> I'm getting some heavy EM interference from somewhere and I can't find out what's doing it. Digital is gone completely, no lock on any channel, even the strongest one.. Analog video is heavily distorted with what looks like 60Hz lines.


First verify if the noise on the analog TV is a horizontal pattern of white dots that crawl slowly up the screen. (Hurry, you've got two days left.) That's classic power line interference.

If the symptoms match, use the AM radio in you car or a battery operated AM radio to locate the source. To do it, find an unused frequency between 530 and 620 kHz, and listen for loud buzzing. When the buzzing is the loudest, you are close to the source of the problem. If the source is a nearby power line, call the power company to fix it.

Some power companies are extremely responsive to interfere complaints, some aren't. Be prepared to keep calling until you get results. The FCC will step in in extreme cases.


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## SayWhat? (Jun 7, 2009)

Not happening at all so far today. Yesterday was really bad and it lasted for about 12 hours continuous. Everything is the same in the house, all the same devices, motors, fans, etc. running as normal. While it was happening yesterday, I turned each breaker off for a few minutes and none of them cleared the problem.

Makes me believe it's outside somewhere, maybe a bad ground or transformer. Could it be somebody running heavy machinery somewhere else on the grid circuit? Would the utility be able to find something like that?


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## Tower Guy (Jul 27, 2005)

SayWhat? said:


> Makes me believe it's outside somewhere, maybe a bad ground or transformer. Could it be somebody running heavy machinery somewhere else on the grid circuit? Would the utility be able to find something like that?


The most likely cause is a cracked insulator or bad connection on a nearby power pole.


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## jerry downing (Mar 7, 2004)

Tower Guy said:


> The most likely cause is a cracked insulator or bad connection on a nearby power pole.


Rain may make this problem worse.


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## SayWhat? (Jun 7, 2009)

No problem today either so far despite heavy rain last night.

They restrung about a mile of wire and set several new poles in Feb after the Ice Storm. The old wire was copper, the new is aluminum or whatever new alloy they're using now. There are a number of compression splices between the new and old wires. My service drop and transformer did not come down and were not replaced.

When I talked to the utility yesterday they asked if this problem occured before the storm, but I honestly can't remember if it did or not.


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## SayWhat? (Jun 7, 2009)

Looks like it may be a cable issue. When it's hasppened in the last few days, I've disconnected and reconnected the cable from the antenna at the amp and it clears. If I was dealing with a transmitter, I'd be checking SWR, but I've never heard of that being a problem on receive only systems.

I may try rerouting some of the cable and see what happens.


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## n3ntj (Dec 18, 2006)

Are you using RG-6 quad shield cable? That should do a good job. No way to really check SWR easily on a RX only setup. Are you near a transmitter site of a local radio station? Are there any CBers or hams near you? Take a look around the neighborhood for antennas (yagis, dipoles, verticals, etc.). My next door neighbor's garage door opener has a spurious emission problem.. when she opens/closes it, my alarm clock radio gets all noisy.

Locating an EM issue can be very tough..something as simple as a small motor could be the cause, and there are small motors all around us.


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## jimmyv2000 (Feb 15, 2007)

This may sound stupid but its fact.Do you have a cell phone?
Some Phones that *AT&T* and *Sprint* use Do cause interference sometimes on AM radio.
I had this issue a few years ago and when i switched to *VERIZON WIRLESS* my interference issue went away.


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## no static at all (Jan 17, 2009)

jerry downing said:


> Rain may make this problem worse.


I have found the exact opposite to be true. The power line/transformer induced electrical interference decreases(sometimes disappears) during periods of rain or high humidity.


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