Net Result of Snowden

[jdb10987 at yahoo.com (jim bell)]

 From: Beaker Meeps <beaker at dropperbox.com>
On 2/14/2017 2:04 PM, jim bell wrote:
> *From:* Ryan Carboni <ryacko at gmail.com>
> 
>>I have written down so notes on the movie. Also, my cell phone works
> fine in the microwave.
> 
> You might be very near a cell-phone tower.
> 
> Try putting a large plastic or glass container of water in the
> microwave, with the cell phone.  (say, 1/2 gallon of water.)
> A microwave cavity, alone, is fairly well-shielded.  But it is also
> very low-loss without a "load", an object within it that will absorb the
> 2.45 GHz microwave energy.  Usually food, of course.
> 
> One thing that would be useful is an app which showed the received
> signal strength for that cell phone, to a resolution much better than
> the usual 5-bar display.  

>Well put. Â Â 
A good radio receiver can have a dynamic range of 100 decibels.  (or, a 10**10, a factor of 10 billion) range over which a signal can be input and still give a useful, even good-quality result. http://www.radio-electronics.com/info/receivers/dynamic_range/dynamic_range.php
I could not quickly find a figure as to the typical shielding provided by a microwave oven, but let's suppose it's 60 db, or a factor of 1 million reduction. Â You can see that if the signal outside the oven is, say, 80 db over the minimum detectable level, putting it into that oven would reduce it to 80-60db, or 20 db, still a very useable signal. Â Thus, it would appear that the phone works fine in that oven. Â Adding a large container of water into that cavity could further reduce the signal level.
Also, be aware that the effectiveness of shielding in a microwave oven may be frequency-dependent.  In some cases, I have seen a "channel" within the door-seal structure that I suspect is designed to oscillate at a microwave oven's frequency:  2.45 GHz.   Thus, it blocks that signal, but it might not do so well at blocking at a typical cell phone's frequencies,  900 Mhz, 1800 Mhz, and 1900 MHz.    https://en.wikipedia.org/wiki/Cellular_frequencies ;     Combining use of a microwave, with wrapping a phone in a couple layers of aluminum foil, should work okay to block it.  �   

         Jim Bell

For the curious:

https://www.thenakedscientists.com/forum/index.php?topic=41755.0

tl;dr - frequency bands are different. Although some get lucky because
of the wall density.




   
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