Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not
even sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

Try tinfoil, and see if that works.

A more expensive approach would be to replace the CRT with
an LCD.

Aidan Grey


On Sat, 18 Dec 2004 16:35:27 GMT, Adam wrote:

Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not
even sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

There is no such thing as a magnetic insulator. Magnetic shielding is highly
permeable which gives the magnetism an easier path to follow. Copper,
aluminum, etc, non ferrous materials do not work. The best material is Mu
metal, and yes it will cost a limb or two.
bg
Adam wrote in message ...
Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not
even sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

"bg" wrote in message ...
| There is no such thing as a magnetic insulator. Magnetic shielding is
highly
| permeable which gives the magnetism an easier path to follow. Copper,
| aluminum, etc, non ferrous materials do not work.

Untrue. The eddy currents buck the magnetic field - imperfectly, but at a
much lower cost than mumetal. A sandwich of alternate layers of aluminum and
steel would probably work better, but the OP wanted cheap and easy things to
try.

N

As I earned a living for many many years doing EMC, I think I am fairly
well-quailfied to comment. This will be a long response because it is
a complicated subject.

There are magnetic chields available for TVs and monitors, but they
cost almost as much as getting a new LCD type monitor/tv set.

First, you have to find out if the magnetic interference is coming from
the actual radiatior or from unbalances in the house wiring. Is the
heater one that uses a wound element that glows, like a giant toaster,
or is it some other type? Does it run on one 120 volt phase of a
3-phase system, or on 240 volts or on 120 volts? Anything that runs
on one phase of a 3-phase system causes unbalances in the circuit that
can cause the problems you are describing. Frequently, the problem
occurs if the power lines are run as Romex, rather than in steel
conduit which does provide some first-order shielding.

But, if there is a power transformer feeding the building that you are
in, and you are within 20 or so feet of the transformer, there might be
enough magnetic leakage from the power transformer to cause your
problem. These transformers are usually located in the basement of a
building due to their size and weight. It actually takes a very small
field to cause waviness in a crt display. The earths magnetic field
will even influence a CRT display. If you take a monitor with a fixed
display. and rotate it 90 degrees, you will see a noticeable
movement/displacement in the picture (typically about 1/8 inch). That
is due to the static (DC) earth's field.

If you can get your upstairs neighbor to cooperate, you could use
telephones or cellphones and arrange for them to turn on their various
heaters to see which one(s) cause the problem. Then, if the heater is
not quite close to your monitor, it is mostl likely wiring currents
unbalances that are your problem, and then your landlord might also be
concerned.

Let me know what you are able to find out, this process typically takes
several hours of on-site investigation to resolve, so via internet
should/will be even slower.

H. R. (Bob) Hofmann

The only technically easy way to shield for magnetic interference is with a
magnetically soft material. The best is something called "Mu-Metal" which is
also very expensive and difficult to work. Sheet steel might help
some but realistically, moving the monitor or going to an LCD display
are the only practical solutions. Tin foil won't do anything except make
your monitor look strange.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

"Aidan Grey" writes:

Try tinfoil, and see if that works.

A more expensive approach would be to replace the CRT with
an LCD.

Aidan Grey


On Sat, 18 Dec 2004 16:35:27 GMT, Adam wrote:

Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not
even sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

"Sam Goldwasser" wrote in message
...
| The only technically easy way ... Tin foil won't do anything except make
| your monitor look strange.

If you wear it on your head you REALLY look strange!

N

Adam wrote:
Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not even
sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

An LCD monitor would probably be cheaper and more effective than
shielding.

But I rather doubt the magnetic field from an electric heater is that
strong. Are you sure you're not having a brownout +/-?

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

"CJT" wrote in message
...

| An LCD monitor would probably be cheaper and more effective than
| shielding.
|
| But I rather doubt the magnetic field from an electric heater is that
| strong. Are you sure you're not having a brownout +/-?

Maybe he has a neighbour with a CB set and a 2 KW linear?

N

CJT writes:

Adam wrote:
Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's
apartment.
Apartment living sucks. If the upstairs neighbors toddler isn't
running laps they have one of the lovely wall mounted electric
heaters running. While acousticly quiet they do produce quite the
magnetic field. Now that it's winter here in the northern
hemisphere there are at least three heaters close enough to my desk
not counting my own to induce waves in the picture of my CRTs.
I was thinking about approaching the neighbors and requesting that
they quite using their heaters but I have my doubts about that
working. The next thought I had was moving my desk but like many
apartments, this one is pretty small, there isn't really anywhere
else to put it (my girlfriend won't let me put it in the dinning
"room") and I can't afford to buy a house quite yet (too bad, the
market is pretty good right now). It would seem that the only
solution left is shielding but I'm not even sure how possible that
is.
What materials would not only work but wouldn't require me to sell
any appendages?
Thanks and sorry for rambling.
--adam

An LCD monitor would probably be cheaper and more effective than
shielding.

But I rather doubt the magnetic field from an electric heater is that
strong. Are you sure you're not having a brownout +/-?

I doubt it's from the heater but more likely from an unpaired conductor
in old wiring.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

Another approach - completely different...

You could run your monitor at 60Hz vertical frame rate. If your 60Hz
matches the line frequency, you won't see the interference. Chances
are the two frequencies won't exactly match, but you might want to try
it and see if it is tolerable.

If you can't beat 'em, join 'em.

BTW, I agree that the problem is probably not the heaters. Heaters
don't normally produce much of a magnetic field. Whatever it is, it
is easiest to solve it at the source.

Marko



On Sat, 18 Dec 2004 16:35:27 GMT, Adam wrote:

Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not
even sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

On 18 Dec 2004 19:13:06 -0500, Sam Goldwasser
wrote:

The only technically easy way to shield for magnetic interference is with a
magnetically soft material. The best is something called "Mu-Metal" which is
also very expensive and difficult to work. Sheet steel might help
some but realistically, moving the monitor or going to an LCD display
are the only practical solutions. Tin foil won't do anything except make
your monitor look strange.

Isn't the main difficulty that the metal has to match the magnetic
field in effect?

Tom


--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

"Aidan Grey" writes:

Try tinfoil, and see if that works.

A more expensive approach would be to replace the CRT with
an LCD.

Aidan Grey


On Sat, 18 Dec 2004 16:35:27 GMT, Adam wrote:

Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

Apartment living sucks. If the upstairs neighbors toddler isn't running
laps they have one of the lovely wall mounted electric heaters running.
While acousticly quiet they do produce quite the magnetic field. Now
that it's winter here in the northern hemisphere there are at least
three heaters close enough to my desk not counting my own to induce
waves in the picture of my CRTs.

I was thinking about approaching the neighbors and requesting that they
quite using their heaters but I have my doubts about that working. The
next thought I had was moving my desk but like many apartments, this one
is pretty small, there isn't really anywhere else to put it (my
girlfriend won't let me put it in the dinning "room") and I can't afford
to buy a house quite yet (too bad, the market is pretty good right now).
It would seem that the only solution left is shielding but I'm not
even sure how possible that is.

What materials would not only work but wouldn't require me to sell any
appendages?

Thanks and sorry for rambling.

--adam

"Asimov" wrote in message
...
"NSM" bravely wrote to "All" (18 Dec 04 19:13:08)
--- on the heady topic of " Magnetic sheilding"

What are you thinking, man?! Aluminum is about as good as a piece of
paper in holding any magnetic flux. Perhaps something easily found
like galvanized sheet steel is more likely to work if placed in close
proximity to the device to protect and grounded (to avoid static build
up). Even something like a metal shelf might work but then there is
always the problem of the colour purity being thrown out of whack.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Take a video tape degausser and hold it close to a sheet of aluminium (or
copper). Note what happens. Physics theory will now tell you that the
conductive material is not 'amplifying or enhancing' the magnetic field.
Think it through.

Remember, the OP was looking for 'cheap enough to try'. That does not
include 6 foot squares of 1/4" mild steel plate.

N

"NSM" bravely wrote to "All" (19 Dec 04 19:27:07)
--- on the heady topic of " Magnetic sheilding"

NS From: "NSM"

NS Take a video tape degausser and hold it close to a sheet of aluminium
NS (or copper). Note what happens. Physics theory will now tell you that
NS the conductive material is not 'amplifying or enhancing' the magnetic
NS field. Think it through.

NS Remember, the OP was looking for 'cheap enough to try'. That does not
NS include 6 foot squares of 1/4" mild steel plate.

What you are doing with the bulk eraser is inducing a current by the
conductor cutting the flux lines of a changing AC field/

Self-induction and eddy currents is not the same thing as a material
being ferromagnetic. Aluminum is not in the list of ferromagnetic
materials. Ferromagnetism is the most important property for an
effective magnetic shield.

A*s*i*m*o*v

.... Reactance: your imaginary friend.

The OP writes ---
Not shielding that's magnetic but rather shielding to block those
annoying rotating magnetic field radiating from the neighbor's apartment.

You can re-route the field (mu, steel etc), or cancel it with an equal and
opposite field , but you cannot block magnetism. That's my point.
bg

On Sunday, 19 Dec 2004 23:34:44 -500 "Asimov"
wrote:

Self-induction and eddy currents is not the same thing as a material
being ferromagnetic. Aluminum is not in the list of ferromagnetic
materials. Ferromagnetism is the most important property for an
effective magnetic shield.

Non-ferromagnetic, but conductive, materials are effective magnetic
shields if the material is thick enough and the magnetic field is AC.

For copper the skin depth is about 1 cm at 60 Hz. Since the
conductivity of alum is worse than that of copper, it's skin depth
will be thicker.

A thickness of 1 skin depth will reduce the field by 1/e, which isn't
all that great.

So, I have to agree, that alum shielding would probably have to be
close to 1" thick before it would make much of a difference.

But even shielding with Mu-metal is difficult. By far, the best
solution is to attack the problem at the source.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

"Jim Adney" bravely wrote to "All" (22 Dec 04 19:59:28)
--- on the heady topic of " Magnetic sheilding"

JA From: Jim Adney

JA On Sunday, 19 Dec 2004 23:34:44 -500 "Asimov"
JA wrote:

Ferromagnetism is the most important property for an
effective magnetic shield.

JA Non-ferromagnetic, but conductive, materials are effective magnetic
JA shields if the material is thick enough and the magnetic field is AC.

JA For copper the skin depth is about 1 cm at 60 Hz. Since the
JA conductivity of alum is worse than that of copper, it's skin depth
JA will be thicker.

JA A thickness of 1 skin depth will reduce the field by 1/e, which isn't
JA all that great.

JA So, I have to agree, that alum shielding would probably have to be
JA close to 1" thick before it would make much of a difference.

JA But even shielding with Mu-metal is difficult. By far, the best
JA solution is to attack the problem at the source.


The difference between copper and aluminum isn't so bad because it
works out to be the square root of the conductivity ratio or about 3/4
less here. What is worse is that the equations for skin depth are only
accurate for a conductor thickness greater than 3 skin depths. So
indeed a 1" thickness of aluminum isn't practical even to be found.

A*s*i*m*o*v

.... "Bother!" said Pooh, as he saw the sparks and smelled the smoke.