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Comment by dzhiurgis | Hacker News Reader

> pop it in a microwave oven

Just popped my phone in the microwave oven. Was able to receive a call on 2G as well as 3G.

Huh.

I seemed to recall that Snowden made guests put their phones in the refrigerator, which is the same principle. So I went and tested my phone in on the work fridge, and you could still make calls to it.

Filing cabinet, ditto. Mylar antistatic bag, (which has a conductive layer, though not very conductive) ditto.

Tried some conductive fabric, which we sell for e-textiles stuff, and which the manufacturer's datasheet advertises as providing some 85dB of RF attenuation, and sure enough I couldn't call my phone anymore.

I assumed the fridge was more about "make sure the microphone can't pick up anything from outside" than blocking radio signals.

Yeah I think Snowden said that himself. It was about microphones mostly.

Well lets test that too then!

Switched off, in a tin can, in the freezer. Tin can to block radio signals, freezer to block audio signals. And switched off so the "normal" operation of the phone doesn't drain the battery (i.e.: continually trying stronger signals to reconnect with the GSM/3G/4G infrastructure).

I've done ping tests over wifi here (cell signal sucks at my house, so no way to do that).

Not a Farady Cage:

  * Chest Freezer
  * Fridge
  * Microwave
  * Tinfoil Hat

Faraday Cage:

  * Aluminum Foil Envelope, well sealed around all edges.

Isn't a Microwave a Farady Cage for the frequency used by the oven? I'm guessing the Cell frequencies are different so they can penetrate the cage?

I've retested the microwave, using a 4th gen ipod touch, with 2.4 ghz wifi only.

Just outside the oven, Speedtest is giving me 25ms ping, 10Mbps dl. Inside, with the door closed, it's getting 44ms ping, 1Mbps dl.

I used wifi, since that's what I have access to. Wifi is in the same (rough) band as microwaves. It's probable that the one I tested with was old and crappy with bad shielding. When it's running, it's noisy enough that it will tend to kick any wifi connection from the 2.4ghz into the 5ghz band.

(I live in the boonies, and cell signal is 0 bars till I get out to the road, and even there I really only get texts)

A microwave operates around the 2.4 GHz frequency, so it likely shields only against those frequencies. This is where WiFi lives (in particular the higher channel numbers around 11 and 13). So test the impact on WiFi reception?

Older Wifi uses 2.4 GHz; since 802.11n came out years ago it also uses 5 GHz. Generally 5 GHz frequencies are recommended, when you have a choice, because usually there is less interference.

While we're at it: In the 2.4 GHz range there only are 3 non-overlapping channels: 1, 6, 11. I think 14 also is an option in some countries, not including the U.S.

You probably need to cook it a little more

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