Electromagnetic interference?

Macette

macrumors 6502
Original poster
Mar 5, 2002
472
0
Melbourne
I'm just about to move into a new studio. Problem is, there's considerable electromagnetic interference. My monitor flashes like it's on a really low hz level, and apparently it gets worse...

What can I do about it, short of paying the local power people ten grand to re-wire the whole street?

Does the problem affect LCD monitors as well? I'm considering trading up, and that would be a really good reason to do it...
 

richierich

macrumors newbie
Jun 14, 2002
17
0
london
i am not sure if this is correct or not but in the studio here we have 2 crt's going crazy over electromagnetic interference whilst the guys on notebooks don't seem to have any problems!
 

iwantanewmac

macrumors 6502
Oct 24, 2001
356
0
A bit off topic but.....my mouse freezes if my cellphone is next to it and I get an incoming phonecall. :)


(why the hell did I post this?.......................)
 

King Cobra

macrumors 603
Mar 2, 2002
5,403
0
I'm not sure if this is going to help any, but there are electromag. fields about around monitors and stuff. (First, I'm assuming you know how a CRT works.) When I got my CSW 4.1 Speaker/Sub system I read in the directions that the subwoofer should be placed at least 15 inches away from the monitor (for our metric friends, about 38cm). I think what happens is when you have different appliances that use the same frequencies for incoming/outgoing signals for whatever purpose, such as lighting up a monitor or to emitt sound, the waves can interfere and cause a disturbance.

If there is a way to put the monitors far away enough from the electromagnetic interference you should be fine.
 

Mr. Anderson

Moderator emeritus
Nov 1, 2001
22,407
0
VA
do you know where the em interference is coming from? you can do some things to reduce it, by constructing a Faraday Cage out of chicken wire and see if it has any effect. But you might only need to put up a wall of conductive material - again the chicken wire on the side of the room facing the street-if that's where its coming from.

Are the monitors the only thing being affected? Could it also be the powersupply?

D
 

Mr. Anderson

Moderator emeritus
Nov 1, 2001
22,407
0
VA
Originally posted by King Cobra
I'm not sure if this is going to help any, but there are electromag. fields about around monitors and stuff. (First, I'm assuming you know how a CRT works.) When I got my CSW 4.1 Speaker/Sub system I read in the directions that the subwoofer should be placed at least 15 inches away from the monitor (for our metric friends, about 38cm). I think what happens is when you have different appliances that use the same frequencies for incoming/outgoing signals for whatever purpose, such as lighting up a monitor or to emitt sound, the waves can interfere and cause a disturbance.
your subwoofer has a very large magnet in it - have you ever placed a magnet on a crt screen? weird stuff and don't do if for very long, it will remain for a while - I've had one last for over a week.

the thing about the frequencies and interference has to do with lights and monitors, not sound. If you have a 60Hz light and your screen set to 60 Hz, there will be problems - even if you have it in the 60s at all - its best to put it above 70 Hz to aviod any obvious interference patterns.

D
 

Sun Baked

macrumors G5
May 19, 2002
14,874
57
If the place has motors and/or florescent lights wired to the same panel as the rest of the circuit, you can be getting a lot of noise. Unbalanced power supplies coming off the panel will also cause problems. An industrial complex in the same neighborhood can also cause a lot of line noise.

Then there are the places that continually run under voltage, over voltage, have bad grounds, etc.

So if it's not a magnetic field, and is actually a case of bad power then you'll likely need to spend some money on a good line conditioning UPS. Or call in an electrician to run a clean line with a solid ground.
 

Macette

macrumors 6502
Original poster
Mar 5, 2002
472
0
Melbourne
Thanks for all the help!

What is a faraday cage?! The studio is, coincidentally enough, in a street called Faraday Street. So that could be the answer... How do I make one?

I think the interference comes from having uninsulated power line clusters in the street outside. The city power company have checked it out, and say that's the probable cause - they could fix it, but they'd charge US ten thousand bucks to do it, so it's just not going to happen. We've also got tram lines running down an adjacent street, which people say can be difficult (but ther'es hardly a street in inner Melbourne where that wouldn't be a problem)
 

Mr. Anderson

Moderator emeritus
Nov 1, 2001
22,407
0
VA
You might not need a Faraday cage, but make one big enough to fit around the monitor that's giving you the problems and see if it fixes it, if it doesn't then the issue is the power supply and you'll need to get a UPS.

Buy some 1cm openning chicken wire, you don't need much, and make a box out of it big enough to fit the monitor in. feed the plugs through and plug it in, turn it on and see what happens. Rememeber, this is just a test, I'm not saying you're going to have to do this to use your computer.

If it fixes the problem, well, you'll need to line the wall facing the street with more chicken wire - and it might take more walls to get it to work correctly. But what this will do is effectively ground the electromagnetic fields generated outside.

Let me know what happens, and pics would be kind of fun.

D
 

AlphaTech

macrumors 601
Oct 4, 2001
4,556
0
Natick, MA
You should also consider getting a good quality UPS for your computer.

Have you considered getting a foil cap for yourself (and maybe your computer)??? You know the type, it's just like the "crazy people" in large cities wear to stop the spy satellites from getting into their heads. :D

Hey dukester, does the chicken wire need to be grounded or something, or is it's presence enough to stop the EM field from making his monitor it's biatch? What should he do on the windows?? I think it would look nuts to have the wire covering the wall, and going over the window as well. :D
 

Mr. Anderson

Moderator emeritus
Nov 1, 2001
22,407
0
VA
I found a somewhat technical description of one online - but its not too much.

http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/E3/

The Van de Graaf gernerator is a device that creates a high static electricity charge and most schools use them for demonstrations.

If it really is an EM field interference, it will require a bit of tweaking to get the best results. Just like its hard to get cell phone reception in buildings, metal can obstruct the fields, but a cage might not be necessary. And even a partial wall of chicken wire would have some effect, but that might have to be grounded.

But try the small cage around the monitor first - you might want to make it big enough to fit the computer in as well - and see what happens.

And take pictures!

D
 

Mr. Anderson

Moderator emeritus
Nov 1, 2001
22,407
0
VA
I never knew macette was a she either., until she explained her name in the 'where'd you get your username' thread.

mac - ette

that make it easier?

but her sig should have been enough!

D;) :D :eek: