[TCML] of Faraday Cages and Cell Phones

[dave pierson <dave_p@xxxxxxxxxxx>]

[At discretion....]
While cell phone freqs are well removed from Tesla Coil
freqs, an understanding of Faraday Cages may be of use.

Being a tad puzzled by the observation reported here on
Cell phones in UWave Ovens, i set out to see.

Short Version:
  There isn't one.  trying 5 (five) uWave ovens, in
  2 the cellphone was isolated.  In three ovens it rang.

  First: rural, known weak cell signal: phone disabled
  in oven, rang outside.
  Second: 'suburban', phone rang.
  third-fifth: three ovens at same site, suburban,
  3 and 5: rang, 4: disabled.

  (Since a toasteroven was handy, tried that: rang.  8)>>)

  In each case a random 1in-ish insulator was used to
  get the phone off the bottom of the oven.

  In the 'disabled' cases, the cell system came back with 
  an: 'I Can't find that customer.' message.)  I didn't
  log oven model/serial numbers.

My guesswork, based on past experience: some of the uWave
ovens leak a bit, from age, use.  It would be intriguing to
rerun the sites with a uWave Leak Meter ($10ish  8)>>) 

In a past life i was involved with use/debugging of 'Faraday
Cages' for RF measurement work.  Experience was there are
subtleties, notably:
 long skinny cracks leak a lot: conductive gasket and finger
 stock.

 ANY wire in and out is a source of leakage: filters/shielding
 must be handled with care.   

Faraday Cages at low frequency can be penetrated by magnetic
fields (eg: power transformers) thick, ferrous material helps.

Constructing a cage good enuf to be a 'three D Strike rail'
is a lot easier.

best

dwp
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