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Author Topic: No hams involved, interesting story. Magnetized steel beams causing problems.  (Read 3950 times)
KF9ZA
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« on: October 07, 2011, 10:53:12 AM »

Ran across this news story. No ham involved, no RFI or EMI.  Somehow during construction the steel beams in the house became magnetized corrupting computer hard drives and distorting TV screens.  This is a new one, thought everyone might find it an interesting read:

http://www.dispatch.com/content/stories/local/2011/10/05/high-court-drawn-into-magnetic-homes-case.html
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AA4PB
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Posts: 12638




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« Reply #1 on: October 07, 2011, 01:10:30 PM »

It sounds like nonsense to me. I wonder what proof they have that the beams are magnetized to the point of causing all those problems? How come magnets in computer speakers or magnetic flux from power supply transformers don't damage hard drives?
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N3QE
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« Reply #2 on: October 08, 2011, 05:20:49 AM »

Working in a building with steel joists for the overall structure and steel studs in interior walls, it is incredibly easy to find spots where a good old color CRT gets distorted. But it's also easy to find spots where it's not so bad (typically away from the walls.) Now that it's 2011... hardly anyone as CRT's anymore, it's all LCD screens in my building.

Steel joists and studs are incredibly common in commercial construction in my area. They may even be required by building or fire code. Residential construction... don't seem so common but some of the larger homes in the area do have an I-beam running the length of the house and serving as a joist.
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KF7CG
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« Reply #3 on: October 08, 2011, 06:39:44 AM »

AA4PB

Consider this. Speakers and transformers have magnetic circuits which ared designed to contain most if not all of the magnetic flux. In the case of transformers wasted flux is wasted power. Homes and "most" buildings give no thought to magnetic flux during design and it could be quite possible for areas of the structure to have high concentrations of flux it the magnetization of the steel parts of the structure aligned properly by chance.

Did you ever notice, that you could place certain speakers near your CRT monitor and not others and that at one time the better computer speakers were lableled as magnetically sheilded?

Proper sheilding around magnetic hard drives could also help.

KF7CG
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KQ6Q
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Posts: 961




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« Reply #4 on: October 12, 2011, 12:10:00 PM »

The story sounds bogus, even if they did file a lawsuit.  The beams would have to be hugely magnetic to cause the effects they're talking about. I had a house in Nebraska with an I-beam that ran across the width of the house - no problems. It would be interesting to visit the houses with the problem, use test equipment to measure the magnetic field strength. If the beams were magnetized, they're likely accessible from the basement, wouldn't be too difficult to get them DE-Magnetized. It will be interesting  to hear how this plays out.
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N5RMS
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Posts: 37




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« Reply #5 on: October 14, 2011, 12:37:57 PM »

Used oil and gas drill pipe will become so magnetized than it will attract an 8 pound sledge hammer and repell an arc weld.  .....Now how would a beam become magnetized? 
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KF7CG
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Posts: 797




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« Reply #6 on: October 16, 2011, 09:09:17 AM »

Nearby lightning strike anytime near the beam. This could occur any time during its lifespan.

Proper grouping and orientation of one or many beams during a strong geomagnetic storm. Artifacts of storage and tansport conditions.

Proper orientation to a nearby lightning strike is one of the most common. The magnetic effects of a nearby strike and also induced currents can be quite large.

KF7CG
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W8JI
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« Reply #7 on: October 17, 2011, 03:30:37 PM »

Out of all the complaints the homeowners have, only one is possible. That is the destruction of convergence and color purity in a CRT, especially a CRT with a big screen. Even the field from the earth can affect CRTs, and they are easily magnetized.

US TV sets and Japanese sets had a metal mu shield inside that outed the earth's field, and close magnetic fields, away from the face mask and area where the beam was being bent. Cheap later TV's did not.

As for computer drives, cordless phones, and other things...that has nothing to do with metal beams being magnetized. Even aluminum foil backed insulation will stop a cordless phone cold, and the computer drive is far too well shielded to be affected.

I'd bet if someone digs into this they will find the homeowner either can't afford the payments, or they just have buyer's remorse and want a different house or no house at all.

If the builder hires a good consultant the entire case would fall apart.

73 Tom




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K1CJS
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Posts: 5809




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« Reply #8 on: October 31, 2011, 04:59:21 AM »

This just goes to show how big business now thinks its a law onto itself ever since deregulation went into effect.  A document that spelled out exactly what the homeowners can or cannot have the builder fix--not available at the time of the sale?  That is how the story seems to read.  And it also seems that the builder is telling the buyer "Tough cookies, we're not going to do anything for you."

It seems to me that a reasonable fix of the problem could well be done at an expense that is a heck of a lot less costly than what a court trial is going to cost the builder.
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AA4HA
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Posts: 1376




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« Reply #9 on: October 31, 2011, 08:18:36 AM »

Makes me miss my hula-hoop sized degaussing coil I used to have for doing picture tubes. I am surprised that a modern CRT does not have a degauss circuit, usually they are wrapped around the rim of the picture tube and are hooked up to degauss a television screen whenever it was turned on.

It used to be that if you rotated a television to a different position in a room that you could get a color shift. As has been mentioned, Mu metal shields were part of the solution as were the built in degauss circuits.

Kinda cool if you consider just how much magnetic deflection the earth has on an old picture tube. Or if you placed a speaker magnet near a television.

To degauss something like an "I beam" you could rig up something with an arc welder. Just that sometimes when you switch off the AC source it can make the problem worse or reverse the magnetic polarity. Usually degaussers lower the current quickly and do not just cut on and off.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
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