hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

More effective to build a Faraday Cage around the elevator room
(service techs use these for RF tight enclosures).
Jim NN7K

ml wrote:
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

Is it possible to box up the motor? If you can enclose it, you should
reduce most of its noise. Before enclosing it, I would use "RF Paint" to
coat the inside of this box. The govt uses EM-SEC paint for their SCI
projects.

If done properly, you should be able to nullify 99% of that EMI.

"ml" wrote in message
...
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

You would be adding a nice lightning attractor (not lightning rod) with the
grounded copper sheet which if the right conditions occured would also set
your house/apartment building on fire...... According to the ham exam the
intference is their problem. Maybe you could use some ferrite loops/beads
on your power leads to see if you could stop it.
Maybe not theanswer, but it's one way to look at it.


"ml" wrote in message
...
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

"ml" wrote in message
...
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)

First, please know that a mesh is nearly as effective as a sheet -- and
much, much less expensive. I doubt you can afford that copper sheeting.
Can you cover the roof with metal mesh? (Using this principle, I draped some
hardware cloth over my sprinkler valves & wiring and it stopped the false
triggering of the solenoid valves from my 40m antenna. Effectiveness will
vary, depending on the coupling mechanism; coupling via the building wiring
may be as much of a problem as the radiation effects.)

Unless you are creating a true RF-tight enclosure (100dB of shielding
effectiveness is typical for them.) nobody can tell you how much suppression
you'll get, since the situation affects the numbers.

Getting into a struggle with a building owner, especially if it's your
landlord, may be a bad idea. However, he is legally not allowed to operate
a serious interference source and maybe can be forced to suppress the EMI at
the source. Our local power company, bless their hearts, came out and
completely fixed some power line EMI I had a few months ago. They
appreciate the interference laws but not everybody does.

ml wrote:
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

I'd try bypassing and choking the wires going to the motor and the
controller.

"ml" wrote in message
...
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx
the copper sheet would likely not help shielding of the rf. it would
conduct the currents nicely and maybe redirect the fields a bit, but the
current would conduct out to the edge, right on around to the bottom and
radiate just as well down toward you as up away from you. I would assume
from your reference of an elevator room that this is a relatively tall
structure, so grounding is not going to help. the lengths of the ground
leads would make them also nice radiators for the rf from the motor, perhaps
making it worse if they were close to your antenna. Better to filter power
lines to the motor and controller and stop the noise inside the case... once
its out there is very little you can do to stop it.

In article , Dave
wrote:

ml wrote:
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

I'd try bypassing and choking the wires going to the motor and the
controller.

thanks for the help Dav, i sorta feared a simple sheet wouldn't do
much but wanted to double check

seems the device does not radiate along the power lines it just
radiate s of the device itself

it's about 12x12 x12 inches or so the motor controler is inside a
tight heavey metal cabinet the only rf measured is from that
device itself

my thought is to perhaps find a way to build copper mesh 'box' i
can place over it perhaps that would do the trick? it has to be
mesh as the controller gets pretty hot and is fan cooled

"ml" wrote in message
...
In article , Dave
wrote:

ml wrote:
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i
wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

I'd try bypassing and choking the wires going to the motor and the
controller.

thanks for the help Dav, i sorta feared a simple sheet wouldn't do
much but wanted to double check

seems the device does not radiate along the power lines it just
radiate s of the device itself

it's about 12x12 x12 inches or so the motor controler is inside a
tight heavey metal cabinet the only rf measured is from that
device itself

my thought is to perhaps find a way to build copper mesh 'box' i
can place over it perhaps that would do the trick? it has to be
mesh as the controller gets pretty hot and is fan cooled

galvanized 'hardware cloth' that has about 1/2" mesh is plenty good for that
and can be easily soldered.

In article ,
"Dave" wrote:

"ml" wrote in message
...
In article , Dave
wrote:

ml wrote:
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i
wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx

I'd try bypassing and choking the wires going to the motor and the
controller.

thanks for the help Dav, i sorta feared a simple sheet wouldn't do
much but wanted to double check

seems the device does not radiate along the power lines it just
radiate s of the device itself

it's about 12x12 x12 inches or so the motor controler is inside a
tight heavey metal cabinet the only rf measured is from that
device itself

my thought is to perhaps find a way to build copper mesh 'box' i
can place over it perhaps that would do the trick? it has to be
mesh as the controller gets pretty hot and is fan cooled

galvanized 'hardware cloth' that has about 1/2" mesh is plenty good for that
and can be easily soldered.

thanks Dav, never heard of hardware cloth and wasn't really
sure what the apeture size should be but i'll give the above a try


tnx