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RFI shielded Computer Case

Discussion in 'Computers, Hardware, and Operating Systems' started by W8NGA, Apr 16, 2012.

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  1. W8NGA

    W8NGA Ham Member QRZ Page

    I have a computer in my shack and once and awhile, its affected by RF from my transmitter causing it to "lock up". I been thinking of repackage it into an industrial computer cabinet that may have better shielded than what I currently have. Any suggestions as to where I can find a old shielded PC cabinet made for industrial use?

    Greg W8NGA
  2. N4OGW

    N4OGW Ham Member QRZ Page

    Are you sure the case is the problem? Usually this type of problem is from RF picked up on wires going to keyboard, mouse, network, etc. Try unplugging as many things as possible from the computer and see if it still locks up. Then you can try ferrites on the problem devices.

  3. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    This is true unless you have a case that is plastic.

    I would invest in some snap on chokes and try that fist.
  4. K7JBQ

    K7JBQ Moderator QRZ Page

    Actually, the first thing I would do is try to get the RF out of the shack. Have you tried a line isolator?

  5. AC0H

    AC0H Premium Subscriber QRZ Page

    If it's a Steel or Aluminum case, and 95% of desktops are, you need to bond the case of the computer to the rest of your ground system, the shorter and heavier the better. That should knock a bunch of the RFI down. If it doesn't, start adding ferrites to all the lines coming into and out of the computer, all of them.

    What I did was ground the case to the single point ground buss in the shack, then went and bought several USB extension cables and audio cables. I bought some #31 mix 2.4" toroids and wrapped the entire cable about them so that they are as close to the computer as possible. For those cables that are too big to get a decent number of turns on the toroid I used snap-ons.
  6. K8MCN

    K8MCN XML Subscriber QRZ Page

    are you by chance using a USB hub? that was the culprit in my shack---a toroid around the usb cord from the hub to the PC eliminated the problem--before, just one bit of RF and i had to re-boot...........
  7. KA9JLM

    KA9JLM Platinum Subscriber Platinum Subscriber QRZ Page

    There are some nice rack mount cases available, That typically have good shielding, and are used for Repeater control computers.

    Even the plastic computer cases have thin metal shielding.

    It would be best to eliminate the RF in your shack, than trying to shield the computer better.

    Sometimes a old Filing cabinet makes for good RF shielding, as long as you vent it for cooling.

    But as mentioned it is most likely something connected to your computer, and RF in the shack.
  8. WA9SVD

    WA9SVD Ham Member QRZ Page

    Don't make such a wide generalization. there are plenty of (read: cheap) "plastic" cases on the market that offer little if any shielding, and to make matters worse (at least from an RFI standpoint,) some older less well shielded cases get reused for newer computers. Shielding or filtering the cables coming OUT of (or into) the box can eliminate much of the interference.
  9. KA9JLM

    KA9JLM Platinum Subscriber Platinum Subscriber QRZ Page

    If the computer was sold then it meets some cert for RFI Generation, and has Metal shielding.

    It is better to fix the source of the RFI then to Fix the problems that it causes.

    Devices connected to a computer are the biggest problem for Generating and picking up RF, no question.
    Last edited: Apr 20, 2012
  10. KK4AMP

    KK4AMP Ham Member QRZ Page

    Make sure the case lid / door / whatever makes good bare metal contact with the rest of the case when it's whanged down, even on the industrial rack mount cases.

    Check the power supply 110v connector and make sure it's filtered. Back when I was doing OEM building for a living, we had to show DFI the "disqualified vendor department" as they suddenly stopped using potted filters/connectors, yet the power supply still had the same model and revision number. The only reason we knew is because we suddenly stopped passing our internal FCC Class A tests on our products (Yeah, it was that long ago, no DOCs.), and traced it down to that.

    If you're hellbent on getting a industrial case, these guys are pretty decent:
  11. WA9SVD

    WA9SVD Ham Member QRZ Page

    And you are assuming that everyone buys a "ready made" computer, and no hams build their own? The FCC certificate on a motherboard is meaningless if the case offers insufficient shielding.
    DAPE likes this.
  12. KA9JLM

    KA9JLM Platinum Subscriber Platinum Subscriber QRZ Page

    If You buy a case that is not type accepted then you are buying junk.
  13. WA9SVD

    WA9SVD Ham Member QRZ Page

    Even type accepted cases can be "junk." And may not prevent interference.
  14. KV6O

    KV6O Premium Subscriber QRZ Page

    Or you could get one of these and be TEMPEST/1-92, Level I compliant, just in case your neighbors are trying to snoop on you.

    But, as soon as your hook up your Unshielded Twisted Pair Ethernet cable (and monitor, keyboard, mouse, etc.) all bets are off.

  15. KA9JLM

    KA9JLM Platinum Subscriber Platinum Subscriber QRZ Page

    Very Nice...
  16. KA5LQJ

    KA5LQJ Ham Member QRZ Page

    "Thanks for the suggestions, ahead of time, LOL!


    Thanks for all your suggestions. I don't seem to have any rf ingress from the computer to the
    Icom 706 MarkII-G. That may be due to the 60% nerve deafness in both ears, LOL! But, I'm
    looking for a full tower case and it will be on the floor, yet away from rig. I'll have an IR mouse
    and keyboard, so I won't need those extender cords, but I will put on the ferrite cores to
    make double sure that it it's protected.

    I'm looking for a quad-core processor on the board with on-board sound and video. I hope to
    have back-up audio and video boards to install as well. If possible, I'd like as much RAM that
    will go in the slots, which should make Linux =scream when it runs, LOL!

    On the tower case, I don't want any clear plastic side to see into the computer. To me, it just
    opens up a case of snakes for rf to get through. I'll need to put a lot of fans to blow out or in
    to keep the innards cool so they operate better. Water or freon cooled cases are way to
    expensive and I don't know how to set them up. LOL!

    As soon as I can, the wife said I could use her old Sony Viao desktop. I'll need to put an
    "after-market" power supply in it as the original 'went NORTH' on me. I think it has 512
    megs of RAM, so it should run LINUX very well, but a bit slow. When I get the 'tower'
    built the Sony will become a 'firewall' with Bastille Linux on it and the tower and my wife's
    new, wireless, laptop plugged into it. MY AVG 2012 ran out of subscription, so I switched
    to ClamWin.

    Well, it's 2:15 PM (1915 Z) and time for my Sunday nap. Enjoy the day, I know I have.


    Last edited: Apr 22, 2012
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