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How are the Baltimore riots going?/Any way we can help?


>> On Sat, May 02, 2015 at 06:21:16PM -0600, Mirimir wrote:
>>> For the Faraday bag, see
>>> <http://www.instructables.com/id/RFID-Secure-Wallet/>. It's easy to
>>> test. Just put the phone in the bag, and call it. If it rings, there are
>> >leaks.

>> I am noob at smartphones, but isn't this very close to
>> functionally equivalent to just physically remove the
>> battery from the phone?
>> At what distance is phone with removed battery detectable?
>> Well, if someone implanted "backup battery" this fails,
>> but the implanted battery must be sufficiently small
>> to not see it.>I don't know enough about smartphones to say. The effectiveness of
>removing the battery may vary among devices. Snowden told people
>visiting him in Hong Kong to put their phones in the refrigerator, which
>is a Faraday cage. Also, using a bag is arguably less hassle than
>removing the battery.
For an RF-shield, I think that using a microwave oven would be much superior to a refrigerator.  By definition, a microwave oven is designed to contain a huge (1 kilowatt) emission of 2.45 GHz signal (close to those of cell phone frequencies, some are 1700-1900 MHz), so that humans can live with reasonable safety a foot or so away from it.  This implies a shielding of around 60 decibels.I'd keep a container of water inside the microwave cavity to absorb emitted microwave-band signals.  (And, of course, you should detach the power-cord of the microwave, to avoid accidently frying your valuable electronics.)As for smartphones, my understanding is that most of them don't have detachable batteries.  They do, however, have "airplane-mode" function, where (presumably) they are set to not emit any signals in any band.  That doesn't mean they couldn't hear, or record, audio, or detect RF signals, for recording and later transmission. 
      Jim Bell   N7IJS             Proudly standing as the LAST "Tech-Plus" Ham (Amateur Radio Operator) in the World.






  
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