Faraday Bags: Necessity or Marketing Hype?

Discussion in 'Wireless & RF Design' started by Raymond Genovese, Jul 12, 2018 at 1:50 PM.

  1. Raymond Genovese

    Thread Starter Active Member

    Mar 5, 2016
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    I was reading this article today.
    Usual lowest common denominator mass media content, with such mind-numbing statements such as "Copying code from key fobs isn’t difficult. And this is something the auto industry and insurance companies are monitoring closely."

    To the point, they mention Faraday Bags. My question is whether anyone knows of some actual tests on the effectiveness of say:

    One of these (~US $58) vs. one of these (~US $1.88) vs.

    one of these
    [​IMG]

    or one of these?

    [​IMG]
     
  2. ian field

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    Apparently some types of the bags are popular with shoplifters.
     
  3. Raymond Genovese

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    Note that EMP bags don't count (read the manufacturer's comments on her web page) :)

    @nsaspook what's the straight poop? Do I need a 3" lead box to keep the evil out?
     
  4. ian field

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    Depends which evil.

    The rise time of EMP is something like 10x that of lightning - a certain size box will be resonant - you might as well hide it behind a slot resonator.
     
  5. nsaspook

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    These things are being sold to the paranoid. Life's too short to tin-foil my car keys.

    IMO most of the EMP(s) hype is balderdash. An effective nuclear EMP attack is a prelude to a full scale nuclear ground attack (from both sides) in just about any possible use. Our nuclear command and control is EMP resistant to the extreme. Decision-makers would not wait to see if an EMP attack lives up to the hype. The Big Red Button will be pressed in an instant at the attacker.
     
  6. BR-549

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    Does your FOB work....wrapped in foil?
     
  7. Raymond Genovese

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    I was interested in whether or not some good tests have been conducted to compare the various devices with their ability to prevent transmission by that device. To cut to the chase, is a tin can as good as an expensive Faraday Bag? That is what I was getting at.

    @BR-549 I have not wrapped anything like a key fob in tin foil, so I can not say. I have, however, wrapped potatoes in tin foil before baking and I believe that doing so provides a more balanced heat distribution.
     
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  8. ian field

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    Apparently the American military has developed an "EMP gun" - A conical spiral inductor/antenna enclosed by a shaped charge. A capacitor discharge is triggered simultaneous with detonation.
     
  9. nsaspook

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    I've seen plans that use a mortar shell for the energy source. For MIL-SPEC EMP hardened equipment the explosive charge would be much more effective in disabling equipment than any possible conventionally generated E-field.
    http://www.amphenol-aerospace.com/pdf/catalogs/Filter_Catalog.pdf
     
  10. Raymond Genovese

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    Apart from EMP "bomb" concerns (which is not what I hoped would be the subject of the thread), the use of some kind of shielding, like a Faraday bag is becoming (or maybe already is in some places) SOP in many forensic situations.

    edited to add: My curiosity is not about forensic uses, but rather privacy and anti-hacking...and it is just a curiosity

    I am curious about the degree to which these bags, as compared to other devices like coffee cans, provide shielding. I am surprised that there are not data all over the place about this issue.

    What I have been seeing is typically something like this:

    "Products geared towards preppers or consumers may not offer adequate shielding or account for forensic needs. Forensics is already difficult - don't leave human error in the picture!"

    Does anyone know about a site that conducted objective tests about the relative shielding capabilities of example Faraday bags, coffee cans, pain cans and the like and actually published the results?
     
  11. Raymond Genovese

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    Here is one example (pdf here). I have not read it thoroughly, but the graphs do not speak well of tin cans and aluminum foil.

    This one (pdf here) looks like about a 3 hour read (for me) but gets into some interesting aspects and, from the abstract, suggests that not all Faraday bags are what one might think they are.
     
  12. nsaspook

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    Good luck finding much beyond the prepper sites.

    Anyone who has a professional EMI/EMC/EMP requirement is not going to be testing Faraday bags, coffee cans, paint cans, trash cans and the like for equipment protection.
    https://hollandshielding.com/RF-shielded-racks
     
  13. Raymond Genovese

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    Actually, having now read the first cite, aluminum foil and a tin box actually looked decent - better than most of the bags tested - against 3G/4G/WiFi, but a single bag tested really looks like it does the job ($30-$300 depending on size, up to duffel bag if I am looking at the right adverts).

    I wonder if the results basically generalize to all of the 'regular' communication frequencies?
     
  14. -live wire-

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    Lowest common denominator indeed. I went onto the website and received ads for sex dolls. :eek:
     
  15. ian field

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    Were they EMP hardened?
     
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  16. -live wire-

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    I didn't click on it!
     
  17. oz93666

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    The good news is that if an EMP comes from a solar event we will have some warning ( assuming the authorities decide to tell us) , should have at least a day before the charged particles arrive ....enough time to wrap all electronics in aluminium foil.
     
  18. -live wire-

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    Yeah. But would that really shield it?
     
  19. ian field

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    8 minutes usually.
     
  20. oz93666

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    Light takes 8 mins 20 sec to travel from the sun ... charged particles from an CME normally take around 1 to 3 days ... so we see the flare and then have some time to shut down satellites (apparently just 'shutting down ' satellites in earth orbit affords some protection) . We can get out the foil... Will foil work ??? Almost certainly , the biggest danger is being connected to long lengths of wire , the electrical grid , telephone wires.

    The biggest ever CME event ever recorded in 1859 took only 17 hrs to reach us...

    "The flare was associated with a major coronal mass ejection (CME) that travelled directly toward Earth, taking 17.6 hours to make the 150 million kilometre (93 million mile) journey. It is believed that the relatively high speed of this CME (typical CMEs take several days to arrive at Earth) was made possible by a prior CME,
    Telegraph systems all over Europe and North America failed, in some cases giving telegraph operators electric shocks.[17] Telegraph pylons threw sparks.[18] Some telegraph operators could continue to send and receive messages despite having disconnected their power supplies...." Wikipedia
     
    Last edited: Jul 16, 2018 at 3:44 PM
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