Big Electricity towers causing CRT disruption?

[sm0kiE]

I wasn't sure where to post this, but this seems like a higly technical situation. I have gigantic electric towers outside my house (mini-Eiffel tower looking things). They must carry alot of electricity, because my monitor image shakes. I use a 21-inch CRT monitor, and the image shakes like mad. The higher the refresh rate, the faster it shakes (less noticable above 120Hz but during peak electricity use hours, it shakes even worse). If I move my monitor to the far end of the house (away from those towers), there is less shaking.

Does anybody know why this happens? I also heard that those poles emit Electric "Fields" that are bad for your health and might damage your genetics or something.

Well, any input is appreciated, thanks.

 

[NeoPTLD]

Originally posted by: sm0kiE
I wasn't sure where to post this, but this seems like a higly technical situation. I have gigantic electric towers outside my house (mini-Eiffel tower looking things). They must carry alot of electricity, because my monitor image shakes. I use a 21-inch CRT monitor, and the image shakes like mad. The higher the refresh rate, the faster it shakes (less noticable above 120Hz but during peak electricity use hours, it shakes even worse). If I move my monitor to the far end of the house (away from those towers), there is less shaking.

Does anybody know why this happens? I also heard that those poles emit Electric "Fields" that are bad for your health and might damage your genetics or something.

Well, any input is appreciated, thanks.

I have had exactly the samething happen when I turn on one of the light. Apparently, the wires in the wall wasn't paired properly causing magnetic flux to leak out of the wall. More than likely, your monitor is picking up magnetic flux from the tower.

Monitors are very sensitive to magnetic field. Some so sen

 

[sm0kiE]

lol, Your post got cut off somehow.

Anyway, does anybody know anything about the prevention of this happening to the monitor?

Also, does anybody know health risks involved with this? I've seen websites say it may cause minor things such as headaches...all the way up to screwed up DNA!!

=(

Can't really complain to the power company OR the city about this, can I?

 

[Shalmanese]

Hmm... for the monitor, encasing it in a faraday shield should fix the problem. In your case, that would mean wrapping it in Al Foil. I have no idea if this would work.

As for the health risks, results so far are inconclusive. It appears that there is more danger living near transformers than near high voltage lines but its hard to fnd a study that doesn't have serious methodological issues.

 

[LurchFrinky]

If you are going to try to shield your monitor you should be careful not to disrupt the cooling. CRTs can put out a lot of heat and you don't want to keep it all inside.

Would a metal screen door mesh work alright as a shield?

I suppose making it look classy is pretty much out of the question .

[edited for spelling]

 

[sm0kiE]

Well, there ARE shields for monitors, but look at these PRICES!

http://www.lessemf.com/computer.html

I have a 21 incher...$850 dollars?? No way!!

Do you think I could compain to the city about this??

EDIT:
By the way, I tried Aluminum Foil....Looks horrible and DOESNT work!

 

[AbsolutDealage]

Originally posted by: sm0kiE
By the way, I tried Aluminum Foil....Looks horrible and DOESNT work!

Yea, if you are actually trying to do the shielding yourself, you are going to have a tough time. Well made functional faraday cages are not cheap.

 

[sleepydj]

wouldn't just degaussing help? I think that's what it's inteded for, right?

cheers,
jimmy

 

[f95toli]

You do not need a Faraday cage, what you need is a shield against magnetic fields (everything below about 100 Hz is basically DC, even a Faraday cage made out of copper is not very effiecient against LF magnetic fields) and that means you need something made out of a hígh permitiivity material such as mu-metal or permalloy.
However, you can also try ordinary iron (iron, NOT steel, steel won't work) which also might work (it is not very efficient).

And no, aluminium won't work since it is basically "transparant" to LF magnetic fields.

 

[PowerEngineer]

While it's certainly possible that electromagnetic fields generated by high voltage power lines might be the cause of your shaking, I'd take another look around the house first. The strength of the electromagnetic fields drop off with the square of the distance (from a line source), which means that strong sources (like the power line) often contribute much less than weaker sources (like electric motors, speakers, microwave ovens, etc.) closer to you. You might try turning electrical equipment near your original location on and off to see if that makes any difference. I'd also be curious to know if a TV set shows the same behavior. Good luck!

 

[sm0kiE]

No, it doesnt seem to affect my TV's. I've moved my monitor to all sorts of places. The three rooms that are close to the poles all exhibit high jitter and waviness, while the room far away has far less/no jitter at all. Maybe it is faulty wiring within my walls, but I doubt three rooms could have the same outcome.

Certain refresh rates, notably 75-85Hz have the most waviness (slow back and forth shaking), while higher Hz such as 120+ have really fast shaking (fuzziness/jitter).

60 Hz is sometimes OK, but sometimes the worst (during certain times of the day). I can't really stand 60Hz anyways.

What is the refresh rate of a TV?

 

[uart]

Hi smokie, I once had a small set of speakers that could be mounted on the sides my monitor. However I found that whenever I did this that it made the image jittery exactly as you describe. I attributed the cause to a magnetic leakage flux from the small power transformer mounted in the speakers.

Both electric and magnetic field will deflect the electron beam in your CRT, causing either jitter or blur depending on the frequency. I suspect that the source in your case is more likely magnetic field rather than electric. Unfortunately low frequency magnetic fields are somewhat difficult to shield, as other posters have already stated.

You could verify that the problem is magnetic as opposed to electric by testing if a "Fariday shield" works. If your Al foil test shield didn't work (AND WAS CORRECTLY GROUNDED = VERY IMPORTANT) then you may assume the problem is magnetic in origin.


As for possible health problems of these low level low frequency EM signals I am personally very skeptical. If there is a link it is very weak indeed and the data very inconclusive despite many large epedemological studies. Workers in many industries (eg Power Distribution industry and many others) are routinely exposed to far greater LF EM field strengths than you'll ever receive in your house from those towers. If there was a serious connection I can say for sure that you'd see large clusters of ill effects in these industries and studies have not found these links. Personally I'd be more concerned about the possible health effects of microwave and mobile phone radiation if I was looking for an EM boggie-man.

 

[Peter]

I've seen the powerline effect. Had a customer who would only buy the finest and best shielded monitors. They were just under the roof of their building, with a powerline running above.
That was in the days when "low radiation" monitors just started popping up everywhere. It was clearly visible that the better the monitor was shielding its own radiation to the outside, the better it was shielded against the powerline field.

I'm living near an electrified train track, about 200 meters away. Yet still, the CRT monitors in that corner of the house all show the 16 Hz flicker induced over to me from the train's powerlines whenever a train is in that particular power segment. Whenever one of those high speed ICE trains is about to zoom by, I see it on my screens before it'll be in sight through the window.

So, these effects do exist, and they're much more long-range than one might think. LCD panel monitors, anyone?

 

[Mark R]

These effects are most likely magnetic rather than EM - as such they will not be shielded by a faraday cage or similar structure.

To shield magnetic fields you need to use a solid shield made of mu-metal, which is why shields that work are expensive and bulky. Alternatively, seperation is an option - unfortunately large currents generate large fields which can radiate a considerably distance.

Computer monitors seem to be very much more sensitive to stray magnetic fields that do domestic TVs - presumably this is due to the much wider range of refresh rates that need support.

 

[Peter]

I doubt the last conclusion - it's just that with TV picture quality being what it is, flickery and miserably blurry, one doesn't notice. On a computer screen that has details, and where the user is focussing on the details, things are much more noticeable.
I'd expect a TV screen to act up even worse, given that TV sets typically aren't anywhere near as well shielded as computer monitors are.

Fortunately, I don't have a TV set in that corner of the building.

 

[Shalmanese]

In the end, it would probably be cheaper just to go with an LCD running on DVI.

 

[Peter]

My point from four posts further up exactly.

Even LCD on analog VGA is perfectly OK, given that today's VGA cables are quite well shielded to avoid them emitting high frequency noise.

 

[OrganizedChaos]

you could always just tear dowm the offending towers.

 

[beer]

Wouldn't it just be the magnetic field that generates the monitor interference? Just have em crank up the voltage :0 Smaller magnetic field!