Massive EMI /EMF problem..any ideas?

[thermionix]

If you can beg or borrow an EMF meter

You can detect ghosts.

Or was it UFOs?

No, Bigfoot!

[Jay]

Well I guess the good news is that when he cuts the power it goes quiet, on the battery radio. Meaning there's noise in his own wiring, so under his control and potentially fixable, unlike dealing with crud from the hotel above.  Hopefully that's also true of the noise in the amps/guitars and he can now narrow it down and fix it.

[dschwartz]

OK some updates on the issue..
i wentthere today and made a few tests..
we built a "faraday cage" with aluminium foil around a big box, and grounded it..

so we powered up everything..and used a single coil guitar..hummed like a beast...then we put it inside the box and.....still hummed like crazy..no change at all..

so..it is definetly electromagnetic, not static or electric field..

so i checked directionality..the least noisy position was with the guitar facing the roof.. , east-west direction was the noisier..

i took my cheap handheld oscilloscope and connected it to a 9v AC transformer to see if there was ripple..nopes, the AC signal was clean as a whistle at 60Hz..

humbucking positions on the guitar worked very well nulling out the noise, though not completely nulling it..

i became obsessed with this problem..i´m sure there´s something to be done about it.. if not, there must be a creative way.. maybe an inverted magnetic field generator to null the field? or using mu-metal as wall paper? (not really  $$$)

[PRR]

> oscilloscope and connected it to a 9v AC transformer

Transformer is a closed loop, rejects 99.9% of external field.

A (single coil) guitar pickup is the perfect exploration loop. You should be able to walk up to the noise source.

[J0K3RX]

Paul was right on with his comment, but that's no surprise... 

So, have you thoroughly checked the wiring in the building?

Is it 220-240 coming into the main power distribution box? Single phase, triple phase, multiple earth neutral etc...?

Check for ground loops in the electrical system? Make sure there is nothing from the previous tenant left over, for example; an old transformer used to power an alarm system left in the ceiling... Is the whole building, every unit sharing a common ground? Is the power transformer supplying the building on a different ground, is the transformer grounded at all? Are there HVAC units in this building? Plenty to look at..

If all of the noise is in fact being caused by an electromagnetic field I would get the hell out of that building ASAP and rent elsewhere!! Wouldn't even try to shield it out... would just get out of that building!

[karbomusic]

>You can shield for magnetic emf...

Mu-metal is expensive and not nice to work with.

Yea, I was about to say, you can definitely shield the store in MU ------ for a million dollars. 

[printer2]

Best advice, find a new location. You have two kinds of fields, electrical and magnetic. You can shield for electrical noise but not magnetic.

You can shield for magnetic emf: http://www.lessemf.com/mag-shld.html - I was getting emf noise from a furman power regulator in my old rack set up. I used the Magnet Shield on the big toroidal xformer in the furman unit to take care of that noise. I've also used the shielding foil when I re-housed ac adapters to use in the same rack. No emf noise. However, for a whole room, I don't think it's a cost effective solution. So I agree, a new location might be a better solution.

Sorry, yes you can shield for magnetic, my answer was looking at the practicality of doing it for a store, even just a room. Not practical.

The copper room, actually a surgical suite with a MRI in it, the walls are wood. The seams of the (thick) copper sheets are soldered to each other. You don't get to see anything like it much so I decided to take a picture before it got covered over.



Can't find a picture but some navy shipboard personnel need to work in the path of FR and radar transmitters. One Mil doc (almost 15 yeas ago I don't remember which) recommendations is that the RF current is limited to less than 100mA per limb. They wear something akin to a mesh suit to reduce their skin being  cooked (think being inside a microwave).

By all means tackle the power wiring first. But if the interference is coming from the transformers there is little you can do to fight it. Doubt the owner will try to solve the problem at its source but I guess it doesn't hurt to ask.

[snap]

OK some updates on the issue..
i wentthere today and made a few tests..
we built a "faraday cage" with aluminium foil around a big box, and grounded it..

so we powered up everything..and used a single coil guitar..hummed like a beast...then we put it inside the box and.....still hummed like crazy..no change at all..

so..it is definetly electromagnetic, not static or electric field..

so i checked directionality..the least noisy position was with the guitar facing the roof.. , east-west direction was the noisier..

i took my cheap handheld oscilloscope and connected it to a 9v AC transformer to see if there was ripple..nopes, the AC signal was clean as a whistle at 60Hz..

humbucking positions on the guitar worked very well nulling out the noise, though not completely nulling it..

i became obsessed with this problem..i´m sure there´s something to be done about it.. if not, there must be a creative way.. maybe an inverted magnetic field generator to null the field? or using mu-metal as wall paper? (not really  $$$)

You grounded it to what ground?