EMI shielding

[metroplex]

How can I increase the EMI shielding in bare bones cases?

I bought a Skyhawk Aluminum case but its got a lot of EMI leaking out.

The HP Pavilion 751N and the Dell Inspiron 8100 I have both are shielded very well.

 

[CaptnKirk]

Round 'Overbraided' cables. You may need to put in a drain wire from the inner shield to a chassis ground point.

At the cable end opposite the attach end for the motherboard, slide back the connector boot and roll the over-sleeve
insulator down to expose approx. 1 inch of the overbraid. Take an approx. 8 in" long peice of wire for each cable,
strip back insulation to approx 3/4", & slip it into the overbraid (a toothpick can be used to expand the weave and form a tunnel),
then roll the insulation over-sleeve back down to hold drain wire in place. Guide the drain wire out from the connector boot,
and strip approx. 3/8" for the contact end. You can crimp a small screw type lug (Auto Parts store) onto the end,
and connect it to the chassis. This is the way EMI is accomplished on aircraft.

*NOTE: Aircraft will actually either solder or ferrel crimp the drain wire splice to the overbraided sleeve, I don't think it's needed here.

SVC has good prices on IDE Cables and Floppy Cables

 

[metroplex]

I was thinking more along the lines of stray EM signals coming from the power supply CPU (high frequency), RAM, etc??

I can't just stick layers of alum. foil on the inside of the case?

UPDATE:

Ordered two ATA/133 copper braided cables and one Floppy copper braided cable.

My AMD XP2200+ system is very dirty compared to my Dell laptop and HP Pavilion 751N - I'm trying to find ways of reducing EMI/RFI emissions.

Thanks

 

[CaptnKirk]

If you have a metal case you have what is in fact a 'Faraday Cage' where it is the terminus of all radio wave interference.

The biggest source of EMI (Electro Magnetic Interference) - Radio waves in fact, are from the wires in the system, with each wire acting like an individual antenna,
either transmitting or receiving a signal. With ribbon IDE cables and floppy cables in a case, there are several hundred feet of wires that act as antennas.
As a mater of fact (2) ATA 133 80 wire ribbon cables at 18 inches long is a total of 240 feet of wire to act as an antenna, the floppy ribbon ads another 50 feet
and you are up to almost 300 feet. Put in a RAID system and you get another 240 feet - and antennas with over 500 feet of wire capture a lot of EMI.
If your powersupply is the big offender (static from those wires), the overbraided round cables will stop that signal from reaching the inner conductors.

If you can capture them either going out from a wire, or coming in from other wires - and run them to ground, you have defeated the 'Cross-talk' and eliminated the interference. That is how the braided round cables work, and if you do the drain-wire mod, they will work even better.

 

[metroplex]

I heard excessive RF leakage can cause health problems.

My case is aluminum - with a plastic front bezel.

 

[mechBgon]

Aluminum is metal, and unless the case is unusually designed, there is a layer of metal behind the plastic bezel.

Incidentally, Coolermaster is putting out some rounded cables with the drain wire already in place. If you haven't got any rounded cables yet, might get those ones: floppy cable and IDE cable.

If you're looking for ways to cut down exposure to radiation, maybe an LCD monitor would be a good place to start, if you don't have one already.

 

[CaptnKirk]

Great call Mech - those 'Drain Wires' are exactly what I was refering to in the 'How-to-Mod'.

Another way to cut down on radiation exposure would be to wear lead underware.

 

[metroplex]

WHat should the layer of metal look like behind the plastic bezel?

My casing has a metal chassis but the front bezel has ports where there's no shielding.

Those cables are a tad too expensive... $30 for a pair of IDE cables and $12 for the floppy!

 

[CaptnKirk]

Do the mod yourself with cables from SVC, the wire & lugs are about $ 2.00, might take you an hour on them.

The case front still has enough metal for EMI shielding - this isn't like a nuclear reactor, probably not even as much as a cell phone puts out,
and the cell phone is made to be a transmitter.

Don't go out jogging wearing the lead underware.

 

[metroplex]

Can I use a wire that's soldered/strapped tightly to the braiding and connect that to the chassis?

Or is that what you recommended I do?

 

[CaptnKirk]

You are correct. All you need to do is make contact to the braided shield with a wire, and run the other end to anywhere on the chassis.|

 

[everman]

Originally posted by: CaptnKirk
Great call Mech - those 'Drain Wires' are exactly what I was refering to in the 'How-to-Mod'.

Another way to cut down on radiation exposure would be to wear lead underware.

Nice tip!

 

[metroplex]

Ah i see!

So what lugs are you referring to that I can get at an auto parts store?

I'm a car nut too - but I'm not familiar with this part. I might recognize it when I see a pic, but when I hear "lug" I can think of a thousand things that might fit your description.

What gauge wire should I use for the drain?

Also what method of attachment to the chassis is recommended?

Thanks for the tip!

 

[Dud3]

What do you do about the lead in the underwear though? I'll take my chances with EMI (In fact, I'm making a case with acrylic panels, so I'm not that concerned).

So what bad and nasty things does EMI do? Is it better or worse than a poorly shielded microwave oven?

 

[Bad Dude]

The conversation here is way beyond me. However, I am very interested in shielding my case b/c everytime I turn the computer on, I cannot watch TV and I have a very strong amplified antenna. What is the cheapest and best way to shield my case? The thing is that this only happens with my main computer. The other computer does not interfere much with the receptions?
Thanks for the help.
A good link would help my understanding.

 

[CaptnKirk]

This will help with the TERMINAL LUGS and the wire should be 26 - 28 Ga.
Most Automotive stores, Pep Boys, Auto Zone, Etc., and Fryes will carry the tools, lugs, and wire.

You don't need to solder at the overbraid attach point unless you get real ambitious.

Additional Information

 

[Jeff7]

Originally posted by: Dud3
What do you do about the lead in the underwear though? I'll take my chances with EMI (In fact, I'm making a case with acrylic panels, so I'm not that concerned).

So what bad and nasty things does EMI do? Is it better or worse than a poorly shielded microwave oven?

A poorly shielded microwave will probably cause noticable problems, and would be considerably more dangerous.
As for RF radiation, there doesn't seem to be anything conclusive yet to show that they cause health problems. You get bombarded with radiation when you go outside or turn on a flourescent light.

 

[metroplex]

Yeah but when you go outside or turn on a fluorescent, its not the same amount as a cell phone or EMI/RF from a dirty computer.

Call someone on your cell and put it next to a radio that's tuned to a low signal AM Station. BZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ


BTW Kirk: Oh i see, I have those lugs. I was asking about how to attach the wire to the overbraid - do I solder them or strip the wire then use nylon tie wraps?? I just need to make contact with the braiding right?

I was thinking about using 18 AWG w/ some spade connectors.

 

[CaptnKirk]

Re-read post#2 - the 'Spades' will work. braid contact is enough, solder not req'd, unless you want to.

Send pics if you can so we can see results

 

[Bad Dude]

So captain. Where exactly do you connect your wire to ground it? Exactly where on the IDE cables, and how? Do I actually have to strip the IDE cable plastic off and connect the ground wire directly to it?
Other than the cables, is there anything else that need to be grounded, I mean out of ordinary?
Thanks.

 

[CaptnKirk]

All you are doing is adding a drain wire to the overbraided sheild.
The captured RFI is routed by the drain wire to ANY ground point within the chassis.

You DO NOT go into the IDE inner conductors at all.

Once you have contact with the overbraid via the drain wire,
the loose end gets a lug on it and it can be attached to any metal part of the interior of the box.
A good place would be with a screw that is used to hold in or retain one of the CD type drives,
or even a HDD. Just put the screw through the lug before securing to the mount.

 

[Bad Dude]

OK. Let's see if I get this correctly:

1) I must have the braided cables. Can I not use the regular ribbon cables?
2) Just get a drain wire to contact the overbraided shield and connect to case chases. The thing is, I don't get what you mean by overbraided shield? Do you mean the cables that cross each other and leave on the plastic and get a cable to run the ground to it without stripping to the bare copper? Also, what kind of a drain wire? The one that is bare with copper showing or one with plastic cover around it?
Sorry I don't yet get the whole concept. I should get it soon.
Thanks for your patient.

 

[CaptnKirk]

These are OVERBRAIDED CABLES,
look at the picture and you see the overbraided shield woven around the inner main wires.

MechBegon posted a picture in this thread that shows the drain wire attached to som factory made cables.

 

[Bad Dude]

So I got to have the braided cables? I cannot at all use my regular cables that comes with the Maxtor hard drives right?
Thanks .
I will give it a try this weekend.

 

[Bad Dude]

I see the great pictures from Coolmaster. The problem is that I see the ground wire but exactly where that ground wire is attaching to is what I would like to know. Wonder if there is a review somewhere that would disect the cable?

Other than the cables Captain, anything else in the case would need grounding?

Can I just put the aluminum foil around the case and shield it like that? Would that work? Or would it blow up my computer?
Thanks.