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Comment by klondike_ | Hacker News Reader

You should still be able to do this with a cheap RTL-SDR dongle (<$20) and a laptop, though you will probably look pretty conspicuous to the flight attendants

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I think there are FAA or airline rules against passengers on commercial flights using aviation radios -- and those rules might include aviation radios that you synthesize yourself.

https://aviation.stackexchange.com/questions/8939/can-i-fly-...

(It seems that the rules are meant to avoid having unexpected devices onboard using aviation-related RF energy, rather than to prevent passengers from monitoring aircraft communications.)

A passive receiver with absolutely zero emission would allow to listen to pilots communications from the seat and would be easy to build. Listening to the tower once in air unfortunately would not be possible (as with any radio operated in seat) - an external antenna would be necessary for that. The problem with any custom built receiver is however its appearance: a strange electronic device which would probably raise alerts at any inspection, so the diy solution would hardly be doable for use in flight.

But if one can get an old analog FM radio, something can be done eaasily. The air radio band (118 to 136 MHz) is just above the FM broadcast band (76 or 88 to 108 MHz), and airliners use AM modulation rather than FM, but old consumer radio FM demodulators demodulate AM as well, so all one needs to do is retuning the radio on airband frequencies. This can be done by altering some values in the frontend and local oscillator LC stages, but sometimes is enough just to widen the oscillator coil to tune the radio a few MHz up. Nobody should object if you listen to an old FM pocket radio with headphones from your seat.

https://hooktube.com/watch?v=5kvxjNeWMxs

You'd be surprised. I thought the same when I brought 2 arduinos in a makeshift carboard box in my bag and had wires sticking out all over from the breadboard.

Not a word, nor even a wayward look.

> Nobody should object if you listen to an old FM pocket radio with headphones from your seat.

I believe the existing rules would forbid even the use of an FM radio onboard.

That would make sense since a traditional FM radio local oscillator does indeed emit radio frequency, but the level would be really low to be able to jam any of the airplane devices.

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