Re:Why Snowden Asked Visitors in Hong Kong to Refrigerate Th...
by wdavidlee on Saturday August 31, 2013 @04:25PM
(#6307971)
(Full disclosure: I work at Colorado Sensors)
Intentionally building a Faraday cage is really hard.
The major radiation leaks are caused by non-conducting joints at edges of the enclosure. If there are penetrations (e.g., power lines, signal coax, compressor coils, thermocouple wires) then extraordinary measures must be taken to ensure that electro-magnetic radiation remains inside.
It took me about a year to develop a narrow band Faraday cage that achieved > 120dB of attenuation. The secret sauce was gaskets made of Indium and tuned-stub interferometers on each feedthrough.
A typical refrigerator door has a gasket seal that forms a lovely slot antenna. I have a 0dBm transmitter in my kitchen refrigerator that easily communicates with a symmetric receiver in the basement. The link loss is no more than 30dB. (Online demo at http://www.coloradosensors.com).
TL;DR Refrigerators keep cold air in, but let E&M waves out.
Intentionally building a Faraday cage is really hard.
The major radiation leaks are caused by non-conducting joints at edges of the enclosure. If there are penetrations (e.g., power lines, signal coax, compressor coils, thermocouple wires) then extraordinary measures must be taken to ensure that electro-magnetic radiation remains inside.
It took me about a year to develop a narrow band Faraday cage that achieved > 120dB of attenuation. The secret sauce was gaskets made of Indium and tuned-stub interferometers on each feedthrough.
A typical refrigerator door has a gasket seal that forms a lovely slot antenna. I have a 0dBm transmitter in my kitchen refrigerator that easily communicates with a symmetric receiver in the basement. The link loss is no more than 30dB. (Online demo at http://www.coloradosensors.com).
TL;DR Refrigerators keep cold air in, but let E&M waves out.