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Wrapping in aluminum foil does not make a Faraday cage. Don't believe me? Wrap your smartphone in foil and then call it. Mine rang. Freaked me out when I disc

by ck2 11y ago

Wrapping in aluminum foil does not make a Faraday cage. Don't believe me? Wrap your smartphone in foil and then call it. Mine rang. Freaked me out when I discovered this. It didn't ring when I put it in the freezer though.

jobvandervoort 11y ago
Faraday cages do not block all signals. From wikipedia: > A common misconception is that a Faraday cage provides full blockage or attenuation, this is not true. The reception or transmission of radio waves, a form of electromagnetic radiation, to or from an antenna within a Faraday cage is heavily attenuated or blocked by the cage. However, a Faraday cage has varied attenuation depending on wave form, frequency or distance from receiver. Near field High powered frequency transmissions like HF RFID are more likely to penetrate. Solid steel cages provide better attenuation over mesh cages.
- ck2 11y ago
  You know those old school lead bags they used to use for carrying film through airport x-ray scanners? https://www.google.com/search?q=lead+bag+for+film&gbv=1&prmd=ivns&source=lnms&tbm=isch https://www.google.com/search?q=lead+bag+for+film&gbv=1&prmd... I wonder if that would be far better to almost completely kill a signal.
aaron695 11y ago
Mine rings in the freezer. The theory why Snowden put the phones in the freezer was to block sound. Or he made a mistake.
- ck2 11y ago
  Probably depends on the fridge. Mine is old, really old, like 20 years. Also it probably just reduces the signal, not kill it completely so maybe how close to the tower you are matters too.
rasz_pl 11y ago
you will like this: Can you call a cell phone in the microwave? Physics Girl https://www.youtube.com/watch?v=ot4_jVFXxUU https://www.youtube.com/watch?v=ot4_jVFXxUU
- Unklejoe 11y ago
  I actually tried this the other day with my new Bosch wall oven microwave. It appeared to block the signals enough to prevent my phone from receiving calls, which is what I would have expected from any microwave. I figured a microwave is probably the best Faraday cage that people have sitting right in their house. I'm surprised that the phone in the video was able to receive a signal. I wonder how much 2.4 GHz power is leaking from that thing. A microwave with a bad shield has the potential to leak a ton of power at a frequency that's used by many devices.

by ck2 11y ago

jobvandervoort 11y ago

Faraday cages do not block all signals. From wikipedia: > A common misconception is that a Faraday cage provides full blockage or attenuation, this is not true. The reception or transmission of radio waves, a form of electromagnetic radiation, to or from an antenna within a Faraday cage is heavily attenuated or blocked by the cage. However, a Faraday cage has varied attenuation depending on wave form, frequency or distance from receiver. Near field High powered frequency transmissions like HF RFID are more likely to penetrate. Solid steel cages provide better attenuation over mesh cages.

ck2 11y ago
You know those old school lead bags they used to use for carrying film through airport x-ray scanners? https://www.google.com/search?q=lead+bag+for+film&gbv=1&prmd=ivns&source=lnms&tbm=isch https://www.google.com/search?q=lead+bag+for+film&gbv=1&prmd... I wonder if that would be far better to almost completely kill a signal.

aaron695 11y ago

Mine rings in the freezer. The theory why Snowden put the phones in the freezer was to block sound. Or he made a mistake.

ck2 11y ago
Probably depends on the fridge. Mine is old, really old, like 20 years. Also it probably just reduces the signal, not kill it completely so maybe how close to the tower you are matters too.

rasz_pl 11y ago

you will like this: Can you call a cell phone in the microwave? Physics Girl https://www.youtube.com/watch?v=ot4_jVFXxUU https://www.youtube.com/watch?v=ot4_jVFXxUU

Unklejoe 11y ago
I actually tried this the other day with my new Bosch wall oven microwave. It appeared to block the signals enough to prevent my phone from receiving calls, which is what I would have expected from any microwave. I figured a microwave is probably the best Faraday cage that people have sitting right in their house. I'm surprised that the phone in the video was able to receive a signal. I wonder how much 2.4 GHz power is leaking from that thing. A microwave with a bad shield has the potential to leak a ton of power at a frequency that's used by many devices.