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Comment by bardan | Hacker News Reader

In this video they can apparently hear the transmission by holding a blade of grass against the transmitter https://www.youtube.com/watch?v=b9UO9tn4MpI

The video looks convincing but it could also be faked, and I don't think it's possible. The signal coming into the radio tower (which is basically just a big antenna) would already be modulated to a much higher frequency (702khz or whatever).

I guess there could be some other effect that makes it audible when you hold a blade of grass or a hotdog to the transmitter, but I don't think it would be intuitive.

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"The video looks convincing but it could also be faked"

I don't think it's faked, what's shown here is what you'd expect. I've been on 'live' FM towers and the RF burned holes in my jeans at my knees (my knees were rapped around the metal tower and the induced RF in the tower zapped holes through the material in my jeans and then burned holes in my skin).

On AM the sound that you're hearing is demodulation caused by resistive non-lineararity in the carbon caused by the burning/heating process. This is quite a common phenomenon with high powered AM transmitters.

I've gotten a transmission through my radiator via earth to my computer speakers somehow. With the volume at 0 it still played but was cut when I touched the radiator.

I thought I was going cracy when turning the volume to zero did not cut it before I realized it was radio hehe.

Maybe there can be accidental demodulation somehow?

https://www.youtube.com/watch?v=GHSuInSkHtA

AM is just power, its why crystal radios work...

If you're next to the transmitter, even a wrench can be a receiver. It's a function of power and the am towers put out a shit ton

When there's enough transmitted power, everything turns into a receiver. Besides the infamous tooth fillings mentioned, and the demonstration videos shown around here at the antenna, there's been plenty other reports of things like bedsprings, pipes, and fences converting AM broadcasts into sound.

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