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A comment on What 50,000 watts of RF energy sounds like through a jumper cable. Parent comment

Re:What 50,000 watts of RF energy sounds like through a jump... by plorg on Thursday February 11, 2016 @03:48AM (#11079013)
I have a friend who lives as close as one can legally live to a 100kW FM transmitter. He received a pair of very cheap speakers when he built a new computer but was unable to use them because if they were plugged in the radio signal would come right out of the speakers.

It seemed that the signal path into the speakers was through the input wire (rather than, say, the power cable or the wires between the amplifier and the cone). From what I understand from my undergraduate analog signals course I'm suspicious of the signal actually coming from the transmission tower itself, unless the speakers had just the right configuration to act as a simple diode-rectifier envelope receiver (terminology likely to be incorrect), which I would think of as unlikely for an FM signal.

It may be that the signal came from some other path related to the relaying of the signal from the studio (~1 mi away) to the tower, but I don't know enough about the specifics of the radio station's configuration to say more.

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Re:What 50,000 watts of RF energy sounds like through a jump... by david-given on Thursday February 11, 2016 @04:30AM (#11079162)
That happened to me sometimes, living in the UK --- my computer speakers would come on in the middle of the night and start whispering to me in French. It was exactly as creepy as it sounds.

I think I did eventually pin down which station they were picking up, but I've forgotten now. Interestingly, since I've moved to Switzerland, it's stopped. Maybe the signals don't get through Swiss customs.

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Re:What 50,000 watts of RF energy sounds like through a jump... by rcxdude on Thursday February 11, 2016 @04:47AM (#11079213)
A diode isn't actually required for AM reception, it just happens to be one of the better ways if doing it. In fact, any non-linearity in a circuit will act to demodulate AM signals, as the video and your friends experience nicely demonstrate.
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Re:What 50,000 watts of RF energy sounds like through a jump... by gpvos on Thursday February 11, 2016 @06:25AM (#11079501)
He was talking about FM, not AM. Which makes it rather weird, as you actually need more of a circuit to decode it.
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Re:What 50,000 watts of RF energy sounds like through a jump... by acveilleux on Thursday February 11, 2016 @10:14AM (#11080554)
I had a pair of really cheap computer speakers once that would catch faint FM signal whenever they were powered. I was in a 6th story loft at the top of a hill with a clear view for maybe 30km from my window but not actually close to any transmitter. I blame the 5$ speakers, not the FM transmitter.

That said, I didn't live 300m from 100kw...

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Re:What 50,000 watts of RF energy sounds like through a jump... by eitally on Thursday February 11, 2016 @05:52AM (#11079413)
In college I lived in an apartment near a highway and my keyboard amplifier would pick up CB radio from truckers. I had to physically unplug it at night time.
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