There are lots of possibilities here.

It might be heat-related. I doubt that it's the radon fan, but it could be a thermostat for the attic fan. It could also be the way the sun shines on the outside floods' photocells (if they have them). There could be other items on this circuit that you haven't yet found, too.

You've done well in isolating the noisemaker to one circuit; now you should try to narrow it down further. The next step is to trace the circuit physically if possible, disconnecting everything connected to it, one by one, until you catch the culprit red-handed.

Hi David,
All the things attached to that circuit are wired into it, so I won't be able to figure much out. But.....I discovered the radon fan was just plugged into an outlet in the attic, so we unpluged it. Now we'll just wait several days and see if the interference on the TV is consistently gone.
Do you think this interference indicates that there's something possibly dangerous in leaving it for awhile longer?
Also......while I have you here......if I determine its probably the radon fan, should I call the radon guy back (he installed the fan and the barrier in our crawl space about 8 years ago) or can I just call an electrician? I need the electrician for a couple other things, so maybe he could handle the radon fan too? I just want him to be able to make a decent choice about the brand of radon fan to put in, if I need a new one. Thanks David!

"All the things attached to that circuit are wired into it, so I won't be able to figure much out."

You can still disconnect them, it just is not as easy.
Every item will have a junction box near it or under it.
With the circuit off at the breaker, remove the fixture and disconnect the black wire. Put a wire nut on each open wire end.
Device disconnected.

Thanks brickeyee,
I still wouldn't feel comfortable doing that. But I am going to try to narrow it down more, so the electrician doesn't have to spend so much time searching (and charging!).
Well, my theory about the radon fan fell apart. I had the interference, even with the radon fan unplugged.
I talked with a fellow from our local REMC, and he gave me a few more suggestions, as to how to proceed to figure it out.
He asked if I had an amplifier, and I think we have one in the attic. I will see if we can unplug that and see what happens. (Of course the TV picture won't be as good, but we'll see if the interference is gone).
It just seems that its something that is affected by the heat of the summer afternoons. But I just can't figure out what. Nothing much is running that time of day, and if it is, its been running all day (i.e. a.c., fridge, freezer, pumps for water gardens).
Thanks for your suggestions.

As mentioned before if the outside lights are on any type of electronic switch for automatic turn on the switches can malfunction under certain lighting conditions.
They cycle on and off (if it was a relay it would be called 'chattering') and produce a lot of electrical noise.

Dimmers on the circuit can also cause problems if they are going bad.

No auto lights outside. No dimmers on that circuit. I have to be missing something. I'll keep looking. Thanks.

Think about what appliances operate on timed cycles. Some examples are a self-defrosting refrigerator, a water conditioner (backwash cycle), and possibly a septic aerator.

I had a refrigerator once with a fractured defrost heater; when it was trying to defrost, there was significant current flowing through the fridge frame to ground!

Finding this kind of problem can be a real challenge. There are many appliances in modern homes that you don't notice - or even know about. Electrical devices can be hidden. I've found television antenna amplifiers above drop ceilings and "wall warts" (power cubes) in closets. A friend of mine had a home fire that resulted from the failure of long-forgotten heat tape on water pipes in an attic.

A few years ago we had a question from someone who had noticed the bedroom lights dimming now and then. We had all kinds of speculation about it. A few days later she found the problem, and posted back. It seems she'd had a guest in the spare room recently. The guest had left a flatiron plugged in. As its thermostat cycled on and off, the lights dimmed and brightened slightly. If she hadn't noticed that, the iron might have eventually caused a fire.

The point is that you need to do some sleuthing. Keep looking - you're hot on its trail!

Thanks David,
Your information is very useful to me. You're right....there's lots of things we don't even think of.
I didn't think of the defrost cycle on the fridge freezer. Doesn't that happen once a day? I'll check that out. Isn't the freezer sort of devoid of sound during that time? I'm not sure how else I could check that......maybe with a thermostat set in there?
Question: Doesn't something have to be actually running to cause this problem with the TV?
We have a water softener, that runs about every 4-5 days. But it would have to be actually cycling to be interfering, right?
What I initially suspected was the radio-controlled thing that REMC installed on our water heater, but the REMC guy said its unlikely and it usually only runs in the evening.
One thing concerns me, just because I don't know enough to be scared or not scared about it.......When we moved in here 25 years ago, in the bedroom outlet was this weird transformer-type device, wired into the outlet. We found out it had something to do with the phone out in the barn (maybe the loud ringer??). Anyhow, I eventually had a phone/electrician person come and disconnect it.
Also, we had a buzzer connected to an outlet in the utility room that enabled us to buzz someone in the barn, and later had someone disconnect that. Those wouldn't be causing problems now, would they? There's nothing loose hanging out, but all under the outlet cover plate.
We have several portable phone bases plugged in here and there. We have several computers and printers. We have a TV rotor. We have old baseboard heaters that we never use. We have a manual defrost freezer, several inside and outside GFCI outlets (one of which isn't working, so we don't use it), a safety flashlight that's always plugged into an outlet. That's about it. (But you know I'm probably forgetting about the one thing that's probably causing the problem!).
We remodeled about 10 years ago, and a couple of the guys who did the wiring were a little unfocused, which makes me nervous. We also occasionally have a few mice in the walls, which we usually catch as soon as we hear them.
Thanks for helping me figure this out David!
P.S. We have service to the barn, where nothing is being used, but it does go from there to my chicken coop, where I use a fan most of the time. Would that affect anything in the house?

If your power service is from a transformer that also serves some other customer(s), that could be the source. My rechargeable shaver really causes TV problems while it is recharging. Filters that plug into the wall receptacle might help. Radio Shack has them. You might prefer other sources.

Hi bus driver,
We live out in the country, about 1/5mile off the road. We have a buried cable all that way, up to our own transformer box, which services the barn and the house.
Maybe I'll try unplugging the fan in the chicken coop when there's interference and see if that changes anything.
If it was caused from the fan in a hot coop, would it trip the breaker out there? We have GFCI in the coop and its own power box, which runs from the barn's power box.
Thanks.

Electrical noise can be caused by a lot of things, even slightly loose wiring. The heat in the attic (or other places) can cause the electrical connections to expand and contract, which can create noise problems.

It sounds to me like you have something creating large EMF (electromagnetic fields) in your system during the afternoon. These can be very difficult to track down without proper tools. Some utilities will send someone out for free to survey your home for high field strengths. You might want to call your's to see what they offer.

In my experience, this type of interference can come from another circuit, but appear to be in another. For instance, if you have a poor connection in the wiring for your air conditioner (or any other load that comes on only when it's hot outside) it can create large EMF's that actually induce currents in other circuits, which in turn create the type of interference you are experiencing. When this happens, you would be able find the circuit where the noise is originating, through the process described by many people above, but still might not find the actual cause of the high EMF that is creating the noise in that circuit. It can be very frustrating to people not experienced in identifying and solving EMF problems.

You'll need someone with a gauss meter and experience in using it. They will need to survey the house and associated electric system while the interference is occurring, and when it is not. Eventually, they should be able to identify the actual source, and recommend ways to eliminate the problem. It could be something as simple as re-doing splices, or fixing a simple mis-wiring, such as when a hot wire and neutral wire are connected backwards.

Best of luck to you.

Thanks cpovey and Matt,
Our REMC is very good about helping out on things like this, but it might be more than they want to do....but I could probably talk them into it. They used my house a long time ago to test out EMF findings in a home. Would they just walk around the house with their gauss meter and note higher EMF fields, and then go check more closely around that area?

No, they will need to walk (and crawl) through the entire house and anywhere you have wiring (attic, basement, etc.).

I should have emphasized that I think a loose connection that gets worse with heat is the most likely culprit. Outside lights on a southern or western exposure, and any junction boxes in a hot attic, would be good places to look.

It also could be a poorly wired or poor quality outlet near the TV, including the one the TV is plugged into, that gets just enough extra heat during the afternoon to expand and create a bad connection. Do other TV's in the house have the same problem? You might try a different outlet to see if you get interference there.

I personally do not trust the type of outlet where you just push the wire in the back. I've seen too many of those have poor connectivity. I also find a lot of mis-wired splices, where two or more wires are joined together inside a box. Those wires should form a very tight spiral inside the wire nut, not just merely touch each other side-by-side.

A gauss meter will often find a poor connection without having to open every box and remove every outlet and switch, but not always. You may end up replacing most or even all your outlets and switches, and re-splicing inside all your junction boxes, and even then there's no guarantee it will be fixed. Someone with experience with this type of work can usually find and fix the problem, however. It ain't rocket surgery, but it isn't easy either.

I had one case like this, and it ended up being a kid operating an old cb radio in his room after school and after his summer job every day. The radio had a short to ground and gave him a shock whenever he touched the metal casing, but he kept using it for months and months, just listening to the truckers on the highway.

Thanks Matt.
It happens on every TV in the house at the same time. In case you didn't read it above, there is one circuit breaker that, when I turn it off, the interference stops. Sometimes it stays stopped when I turn the breaker back on and other times it starts up again a short while later. I'm having the electrician check that tomorrow too, when he comes for something else.
This interference is driving me nuts. I never know when its going to happen. Oh....one interesting thing is it doesn't seem to happen much on weekends. Can't figure that one out. More people are home then than during the week. Keep those ideas coming!

"A gauss meter..."

And just how does a bad connection increase the current and resulting fields so a Gauss meter can find anything?

The POCO is not interested since this is not a "large EMF" problem.
Arcs from loose connections create EMI (Electro-Magnetic Interference). The field strengths are typically painfully low.
If you want to go EMI hunting a plain old battery powered AM radio is a better tool.
Tune it between stations and listen to the noise.
It will get louder when you get near the source of EMI.
If you rotate the radio you can find the most sensitive direction for the antenna (it is inside the radio), and then follow it to a source.

Brickeyee......that's interesting, and its something we could do ourselves (with the radio).
The electrician came out this morning for something else and I had him check out the circuit breaker that, when turned off, would often get rid of the interference. He said it was okay, but that there were some loose connections to the service, which he tightened. But he thought the inference was probably from somewhere else. He said he's had situations where interference was from the power line several poles away.

Here in the country, electric arc welding really registers on the TV. I use antenna only. Microwave ovens can be a problem, too.

Hi bus driver,
I live out in the country and have always wondered about someone using something in the area. I use antenna only too.
There is a hog farm next door, and a cattle farm on the other side. Would electric fencing cause a problem? I used to drive by the cattle barn and hear a buzzing noise.
I called one of our neighbors down the road about 1/2 miles away and her TV is fine.....but she is on a different power line than I am.

Brick:
All the major utilities here in CA will conduct a free EMF survey of your entire home, a program that started after the New Yorker Magazine published a series of articles by Paul Brodeur asserting that residential EMF was a huge health problem. The articles were later proved to be largely bunk, but the concern, and the utility survey programs, remain. The state has even set limits for EMF intensity in residences, and adopted a policy of "prudent avoidance" requiring the utilities to design and maintain their systems to reduce EMFs to a practical minimum.

Loose connections are often the source of high EMF in homes. They do not cause "increased current" as you note, but rather rapid changes from zero current to some amount greater than zero. It is the on-off nature of bad connections that create the EMF. These are called "spurious emissions." Far more common, however, are EMFs created by mis-wired circuits or from a source of RF emissions, especially radio signals in the microwave spectrum.

The very definition of EMI is "a disturbance created by electromagnetic radiation emitted from an external source." So, you really can't have one without the other.

Here is a link that might be useful: Definition of EMI

An electric fence really bothers AM radio. Clicks or pops. Farm tractors with gasoline engines create more static from their ignition systems than do automobiles and trucks. Federal regulations affect the licensed vehicles and the vehicle manufacturers design accordingly. Can you video tape the incidents? Certain kinds of static I can identify by sight and sound.

Bus driver,
I'll see if I can somehow videotape it. Its usually 2 very wide lines of static that take up most of the TV screen. And they are so loud you can't hear anything else. Sometimes its constant for long periods of time, and sometimes its on for a few minutes, off for a few minutes. That probably doesn't help much, does it?
No static today....which is unusual. The only difference is: the electrician tightened those "sort of loose" wires in the service box; He replaced a non-working exterior GFCI; it rained; its cooler out.
One thing I just thought of.......we had our power lines buried about the same time that this interference started up. I'm not knowledgeable enough in electric things to even know if that's a silly thought or not.
The talk about EMI above......I hope that doesn't mean that if it is that, we're exposed to high levels of it too.

My take on this is that unless you're standing in front of a radar antenna, you're more likely to be harmed by the fear of EMI than by EMI itself.

My Microwave Oven causes similar interference.
Any chance one is operating nearby?

HTH
Chris

A yes, Paul Brodeur, author of "current of death".
One of th biggest pieces of bovine scatology every put into print.
While arcing can produce EMI, it does not increase the EMF that was present over the non-arcing case.

There has yet to be any evidence supporting any of this junk, and it remains just that, junk science.

The fields induced in your body by simply moving in the earths magnetic field is larger than most fields created by the dreaded power lines (unless you are standing in a bucket truck next to the darn thing 40 feet in the air).

Most of the garbage has gone to the grave of junk science, exactly the right place for it.

"bovine scatology"....lol!
The problem with various pseudo science stuff is that it sounds so good to the lay person. Its the same with some medical stuff, like Lyme disease "research". For the lay person, its really hard to sort out good science from bad. You really have to know and understand good scientific methodology, to know if findings are valid or not, and that's sort of hard for the general public.

I agree, Brick. The EMF scare was just that: a way to attract readers by scaring the heck out of them.

One interesting study, though, showed a slightly increased cancer risk for telecom technicians working in huge switching rooms. This has been backed up in a couple of other studies. If you've never seen one, these places are stuffed with bank after bank of electromechanical or solid state switches, all constantly opening and closing. One theory advanced was that the EMF created by the rapid opening and closing of these switches, plus the constant and very close exposure, led to the increased risk, but as of yet there is no proof of that. Another theory was that because these rooms generally have no windows, perhaps the workers were not getting enough Vitamin D, a very powerful antioxidant that requires sunlight on the skin or in the eye to convert. Personally, I think that theory has more merit.

Another interesting study was of a flock of sheep that have spent their whole lives beneath a major 500kV transmission line in Idaho. This study has been going for about 15 years now, and they found no effect at all from 60hz EMF.

By the way, I started studying this stuff after I became an X10 "expert" way back when. The first generation of those devices were very sensitive to EMI, forcing me to learn about it and figure out how to correct the problems. Poorly wired outlets were definitely the number one problem. X10 still has problems with EMI, but not nearly as much as when it first came out.

Here is a link that might be useful: Vitamin D and sunlight

We had a similar issue last year that took us forever to track down. Then we saw a rerun of the movie 'Signs' and got an idea. As soon as we put one of these on the cat, and positioned him near the TV, all was well.

YMMV.

LOLOLOL! Great idea! I'll put one on the cat tonight!

There have been reports of all power linemen, power house workers, electrical engineers, and phone techs having a higher incidence of brain cancer floating around for many years.
All have used poor (at best) methodology and at best have established a weak correlation.
None has ever identified causation.

There is at least some evidence that transformer oils with PCBs may have played a part.

Very few COs (Central Offices for phones) use the racks of relays and switches anymore. Most are now entirely electronic.
The reliability is much higher for the new stuff. The old stepper relays required large crews and almost constant maintenance to keep them operating, along with a much larger amount of power.

I have supported research (PhD in EE) into EMF effects for a number of projects over the years and not a single one has found any statistically significant effect until the levels produced localized heating of tissue.
This has been the demonstrated mechanism with repeatable results for many years.
Many of the studies outside of labs have used 'wire codes' (go out and count conductors on poles) and other dubious methods to 'gauge' EMF strength.
A few more sophisticated ones have tried actually measuring the fields.
None has produced a decent correlation with field strength or a dose-response connection that has statistical validity.

Hunting with an AM radio works very well for EMI problems at pretty low cost.
I have even used it to scan very expensive systems (aircraft, ships, computer installations etc.) as a quick & dirty check.
After eliminating the most obvious sources you come back with a spectrum analyzer and look for anything else that was missed.

We found our transistor radio and began walking through the house. We haven't taken it to the attic yet, where we suspect the problem the most. But.....where it was the loudest on the main floor was on the wall beside the washer, where there is an old phone jack with a little buzzer attached to it. (The buzzer was to be used to buzz someone out in the barn). There is also a light switch nearby. I don't know much about electricity, but I'm thinking that phone jack with the buzzer probably isn't causing a problem.??
Since the interferrence continues to be only from 2-6p.m in the afternoons, and only on sunny days, its probably from something hot in the attic. But....since we do have this buzzer that goes to the barn, might the hot barn be causing some sort of problem? Thanks.

P.S. The barn is about 150' from the house. It has its own service box and has no other direct electrical connection with the house, except the same transformer.

Where your problem disappears at 6:00 p.m., I have my doubts it's from heat in the attic. In most places in the country this time of year, that's near the warmest time of day. Your attic should be as warm as it is all day then. But sun load may make more sense. It may be something that's exposed to direct sun during that 4 hour period. I know a guy who's TV would quit working during the afternoon and start back up when it "cooled down outside". That wasn't the problem after all. The LNB on his satellite dish was exposed to the sun, would get hot, and break a circuit inside. Once the sun was off the dish, it would cool down and everything worked fine. I feel for you...these problems can be a nightmare to diagnose.

Also, you mention it's only during summer months. That makes me think it's not a mechanical issue such as a bad connection, loose connection, etc. unless that connection supplies power to something that is only used during the summer months. This is sounding more and more like a sun load problem to me since the sun is in a different location during summer months.

Thanks cobraguy,
I'll keep what you said in mind as we continue to try to solve this mystery!

If it IS in the circuit which you shut off, couldn't the electrician just disconnect that circuit and find out what it is?

If there were 10 things on the circuit, I would go to item #5 and disconnect it from there. If the noise stops, then it's from #6 and up. If not, then you'll know it's from #5 and down. Then repeat with #2 or 3. This way you won't need to take all 10 items off the circuit.

If you're having that much trouble with this noise problem and the electrician can't be there when it's actually happening, he could install a switch for you to flip when it does happen.

Are the start/stop times highly predictable (i.e., constant from day to day, always on the weekdays, never on the weekends, etc.)? If so, it's possible that particular leg has become a great antenna (particularly for AM stations due to the length). If the interference is predictable, I would start suspecting an AM transmitting station. Not nearly as likely as heat-induced problems, but still something to consider.