Has anyone tried aluminum or copper foil as a shield?

Discussion in 'Build & Tune' started by Hugh Hemington, Jun 29, 2014.

  1. Hugh Hemington

    Hugh Hemington Well-Known Member

    I know both aluminum and copper foil are supposed to be good RF shields, so I'm wondering why they aren't used routinely in quads where the separation between receiver and ESC can't be increased due to the frame design?

    And is the ESC considered to be the biggest culprit?
    I suppose a powerful FPV transmitter would cause problems too. And would a combo GPS/mag work better if the floor of the pod/dome was lined in foil?
     
  2. Mike

    Mike =) Admin

    I've seen this discussed on other forums in the past. Most theory says it should help, but the experiences I've seen from people who have tried it were split. The ones who said it worked seemed to all use copper mesh to build Faraday cages around the ESCs and sometimes even wrapped the wires. When people say it doesn't help much it probably has to do with the fact that the newer receivers actually do a very good job at filtering the RF interference, so there's not much to gain.

    You can also wrap your wires through ferrite rings.

    http://www.readymaderc.com/store/in...description=1&keyword=ferrite+torroid&x=0&y=0

    You're right when it comes to FPV. There's a whole new set of potential RF interference issues introduced when you add FPV. Most of those issues will cause you problems with your vTX/ video quality though.

    I'm not sure about the GPS, but it wouldn't add much weight, so it probably shouldn't hurt. Again, go with copper mesh, not aluminum.
     
  3. Filipo

    Filipo New Member

    We use a lot of copper mesh - woven wire mesh - along these lines - www.bwire.com

    This allows more flexibility and is extremely durable. Usually very little to no interference, and while it can get a little pricey if you buy a lot of it - it sometimes turns up at local junkyards or hardware stores.
     
  4. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    What is the reason you should not use aluminium shielding? Cat6 cable uses aluminium to reduce EMI, is there much difference to RFI?

    [​IMG]
     
  5. Mike

    Mike =) Admin

    Sorry - that should have probably read: "go with copper mesh, not aluminum foil". I based my post above on general experience and memories of the many arguments on aluminum foil vs. copper mesh I've seen over the years. As said by filipo, copper mesh is much more flexible and durable. Then again, the aluminum shielding in shielded CAT6 cables is metalized (aluminum) mylar, which is flexible and somewhat durable compared to foil, so this is an option.

    I just went and did a good 10-15 minutes of research on aluminum vs copper in general for RF & EMI shielding and the bottom line I saw was that the differences in ability to shield were not too significant, but most people opt for copper mesh for the reasons stated above, and because it's easier to solder to if the application requires it.

    In the end, since weight is the number one concern, on a multicopter, the mylar might actually be the best of all worlds. But then again, as stated above, modern tx/rx typically do a lot to deal with the issue of interference, so shielding is usually not needed at all.
     
  6. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator


    Thank you for clarifying that, I see now that you don't use the foil simply because it is not durable. Thanks for the explanation.
     
  7. Mike

    Mike =) Admin

    NP. Sorry for the confusion.
     
  8. Civenmetal

    Civenmetal CivenMetal

    They should work about the same, as any metal of this type has about the same effect when used as a reflector (a passive element in an antenna system).
    If what you mean is a shield - a box or plate to protect a component against direct radiation - then, again, ali or copper of the same thickness will perform about the same. Copper is always preferred because it has better properties in every area - conductivity, resistance to corrosion, and do on.
    [​IMG]

    If you mean as an earthed protective shield - as above but connected to an electrical earth of one kind or another - then again they perform in a similar manner, but copper is generally preferred. Copper mesh is also a very good RF shield at all frequencies. It’s used for all RF, from HF room shields to computer room shields, and earthed out, to prevent any RF leaking out or getting in, or data leaking out.
    Copper is a ‘better’ metal for use in anything to do with electricity or RF because it is nobler and has less resistance. A simple example is in electric cable (wire), where the standard is copper, but cheap wire can be made using ali. It’s not as good. Ditto for busbars, where copper (plated if necessary) is better than ali or stainless steel.
    Civen Metal mybe help you find the answer, Thanks!
     
  9. Civenmetal

    Civenmetal CivenMetal

  10. dragger201

    dragger201 If it ain't broke, don't fix it??? You kidding?

    Hey Hugh..........now this is all from my understanding..........

    Cross talk or chatter...........is nothing more then a RF generated by one item setting up a sympathetic RF resonance in another device. Most FC now have filtering(anti resonance) devices built in as well as ESCs having a tighter control on RF generation.

    FPV does have the potential for serious crosstalk, but because of the huge gap between 2.4ghz and 5.8ghz it really isn't a problem. However, ESCs and to a lesser extent, FCs and PDBs, can effect the quality of the electrical signal/strength/integrity as they vary the electrical current to the motors. This interference can be controlled by capacitors as well as electrical regulation.

    Nothing beats a copper "faraday cage" for controlling crosstalk, but that's not to say that aluminum shielding is a very close 2nd. Like 95 to 99%. Of all the systems on a quad, the one most sensitive is the GPS unit. But because the RF generated from other systems is so limited in power, it only takes 6 or 8 inches of seperation to eliminate crosstalk problems with the GPS Rx. Or an aluminum shield will work even better at a much shorter distance. I got tired of replacing the mounting shaft on my GPS unit on Frankendrone and am currently using a stubby aluminum mount. I've found that this works better then the "distance" and I don't have to keep replacing shafts when it tips over.............

    Pixhawk.jpg
     
    mozquito1 likes this.
  11. mozquito1

    mozquito1 Well-Known Member

    I don't use anything other than fcb, pdb, rx, vtx. If the board has an LC filter built in, I don't bother. Foil or aluminium works both ways blocking RF.
    I had a quad that was very dirty & tried foil, copper & even aluminium can cut out into a housing around the stack. Nothing worked properly until I put an LC filter on. Basically I don't buy a board now unless it has an LC filter. Most of them do ant way now. But this combined with a few well placed capacitors. Is all you need.
     
  12. RENOV8R

    RENOV8R Well-Known Member

    Believe it or not one of the biggest culprits is our HD cameras like the GoPro, they produce a huge amount of noise. There's a whole thread on RCG on covering them with copper foil copper-sheild-fitted.jpg
     
  13. mozquito1

    mozquito1 Well-Known Member

    Never had a gopro myself, got a sj4000.
    But these don't really fit on anything smaller than a 210. So I bought a couple of the SQ11. Obviously not as good but they suffice & have a neat little stand & weigh about 12g, record in the dark aswell.
     
  14. mozquito1

    mozquito1 Well-Known Member

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