Question about Monitor Shielding at DVinfo.net

Jesse Dorje Irwin · September 20th, 2003, 05:38 PM

I edit on a Mac with a Mitsubishi Diamond Plus 73 monitor, and for NTSC monitoring I've been using the firewire out to a JVC SR-VS30U to a (get this!) Commodore 1084S monitor (which has a very clear picture and I was able to pick up earlier this year, new in the box, for the right price - free!). Anyhow, tired of craning my neck, I recently moved the Commodore monitor within a foot or two of the main Mac monitor. Now I get 'wavies.' It's nothing that stops me from editing, but is there any homebrew solution I can use to shield the interference?

Jeff Donald · September 20th, 2003, 06:48 PM

Put some layers of aluminum foil between the two monitors. That may provide enough shielding.

Mike Rehmus · September 20th, 2003, 07:30 PM

Unfortunately you are looking for magnetic, not electrostatic shielding. That usually takes something like mu-metal which is delicate and very expensive.

Maybe a thin sheet steel enclosure will help but I'd not bet on it.

Jeff Donald · September 20th, 2003, 09:01 PM

Steel works better, but aluminum is usually easier to come by. Aluminum also reduces RF. We used aluminum in several edit suites I designed 4 or 5 years ago.

Mike Rehmus · September 20th, 2003, 10:29 PM

I agree that aluminum will reduce RF as will steel. Assuming they are properly grounded.

Unfortunately the phenomenon that is causing his CRT image to wiggle is a magnetic field put out by the monitor. Only a magnetic or electrostatic field will deflect an electron beam. Electrostatics aren't a factor in this case.

Aluminum will not noticably stop a magnetic field. Sheet steel isn't great but it works somewhat. Especially if it is dead soft like that used in transformer cores.

They shield the CRTs of oscilloscopes (the good ones) with mu-metal which is a true magnetic shield. Enough mu-metal to shield either the monitor or the computer display would be very expensive and easy to damage.

Andre De Clercq · September 21st, 2003, 04:13 AM

Mike, I think you forget the interaction is one of AC magnetic fields. All conductive materials (aluminiun, copper...) will screen off AC magnetic fields too. Magnetic materials will screen off both, AC and DC magnetic fields. Mu-metal is not only expensive but difficult to proces (simple bending without extra thermal treatment makes that the bended zones simply lose their properties). In addition, if used to screen off relatively strong magnetic field it rapidly starts getting saturated and becomes worthless as (DC) magnetic screening material.

Jesse Dorje Irwin · September 21st, 2003, 03:01 PM

Wow, thanks for all your help! I think for now I'm just going to try to find a balance between monitor closeness and interference, but thanks anyway.

September 20th, 2003, 05:38 PM	#1
Jesse Dorje Irwin New Boot Join Date: Sep 2003 Location: Chicago, IL Posts: 5	Question about Monitor Shielding I edit on a Mac with a Mitsubishi Diamond Plus 73 monitor, and for NTSC monitoring I've been using the firewire out to a JVC SR-VS30U to a (get this!) Commodore 1084S monitor (which has a very clear picture and I was able to pick up earlier this year, new in the box, for the right price - free!). Anyhow, tired of craning my neck, I recently moved the Commodore monitor within a foot or two of the main Mac monitor. Now I get 'wavies.' It's nothing that stops me from editing, but is there any homebrew solution I can use to shield the interference?

September 20th, 2003, 06:48 PM	#2
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Put some layers of aluminum foil between the two monitors. That may provide enough shielding. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

September 20th, 2003, 07:30 PM	#3
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Unfortunately you are looking for magnetic, not electrostatic shielding. That usually takes something like mu-metal which is delicate and very expensive. Maybe a thin sheet steel enclosure will help but I'd not bet on it. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

September 20th, 2003, 09:01 PM	#4
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Steel works better, but aluminum is usually easier to come by. Aluminum also reduces RF. We used aluminum in several edit suites I designed 4 or 5 years ago. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

September 20th, 2003, 10:29 PM	#5
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	I agree that aluminum will reduce RF as will steel. Assuming they are properly grounded. Unfortunately the phenomenon that is causing his CRT image to wiggle is a magnetic field put out by the monitor. Only a magnetic or electrostatic field will deflect an electron beam. Electrostatics aren't a factor in this case. Aluminum will not noticably stop a magnetic field. Sheet steel isn't great but it works somewhat. Especially if it is dead soft like that used in transformer cores. They shield the CRTs of oscilloscopes (the good ones) with mu-metal which is a true magnetic shield. Enough mu-metal to shield either the monitor or the computer display would be very expensive and easy to damage. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

September 21st, 2003, 04:13 AM	#6
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	Mike, I think you forget the interaction is one of AC magnetic fields. All conductive materials (aluminiun, copper...) will screen off AC magnetic fields too. Magnetic materials will screen off both, AC and DC magnetic fields. Mu-metal is not only expensive but difficult to proces (simple bending without extra thermal treatment makes that the bended zones simply lose their properties). In addition, if used to screen off relatively strong magnetic field it rapidly starts getting saturated and becomes worthless as (DC) magnetic screening material.

September 21st, 2003, 03:01 PM	#7
Jesse Dorje Irwin New Boot Join Date: Sep 2003 Location: Chicago, IL Posts: 5	Wow, thanks for all your help! I think for now I'm just going to try to find a balance between monitor closeness and interference, but thanks anyway.