5 ms·

The voltage applied to the cable is directly proportional to the audio signal, overlaid on a ~1 MHz carrier. All you need is a mechanism that transforms those v

The voltage applied to the cable is directly proportional to the audio signal, overlaid on a ~1 MHz carrier. All you need is a mechanism that transforms those voltages into vibrations or pressure waves. Presumably, since it seems to happen only when he's striking an arc, it's related to the local heating of the air in the gap ... But I guess it could be electromagnetically induced vibrations of the cable or the tower structure ... There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Not impossible, considering that many AM stations broadcast with 50kW of power (like the one in this video) and can be received across a large swath of the country.

luxflux 11y ago
There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Reminds me of a Gilligan's Island episode, Hi Fi Gilligan: https://www.youtube.com/watch?v=3x1XHv0sxro https://www.youtube.com/watch?v=3x1XHv0sxro
- thwarted 11y ago
  Lucille Ball talking about picking up radio signals in her fillings. https://vimeo.com/72473069 https://vimeo.com/72473069
paulgerhardt 11y ago
That was one specific station - the infamous WLW / W8XO - the first and only US station authorized to operate at 500kW of power.[1] To give you an idea of how powerful that is, take a look at their coverage map: http://i.imgur.com/Aigz1Zh.jpg http://i.imgur.com/Aigz1Zh.jpg The back story is kind of interesting. It was run by Powel Crosley - a sort of 1930's version of Elon Musk. Advertising revenues from the station were so successful he applied to increase the limit from 500kW to 750kW(!). It's a big deal in the ham community, but I only learnt latter that while US stations were limited to 50kW - other parts of the world didn't have such restrictions. Parts of the Middle East have 2,000kW stations. [2] You can get a full download on the Crosley WLW station in this video: https://www.youtube.com/watch?v=CbHjcwIoTiY https://www.youtube.com/watch?v=CbHjcwIoTiY [1] http://www.ominous-valve.com/wlw.html http://www.ominous-valve.com/wlw.html [2] https://en.wikipedia.org/wiki/Transmitter_Solt https://en.wikipedia.org/wiki/Transmitter_Solt
- dnet 11y ago
  Actually, Solt is not Middle East, but in Central Europe. (I live ~50 km from it.) But yes, it's 2 MW, and at night, it can be heard using conventional receivers as far as Belgium.
  - paulgerhardt 11y ago
    Corrected link: http://www.engineeringradio.us/blog/2012/12/the-continental-d323c-medium-wave-transmitter/ http://www.engineeringradio.us/blog/2012/12/the-continental-...
- gambiting 11y ago
  Well, the Warsaw Radio Tower used to be the tallest man-made structure in the world until it collapsed due to a guy rope failure - and it had a 2 megawatt transmitter, it could be received literally anywhere in the world: https://en.wikipedia.org/wiki/Warsaw_radio_mast https://en.wikipedia.org/wiki/Warsaw_radio_mast
- michael_h 11y ago
  I grew up about 5 miles from that antenna. I can't say I ever heard the radio through the wiring in my house. The Voice of America antenna array down the street though? I could hear it clearly through my stereo speakers when everything was turned off. It's been dismantled, but I can imagine the number of ghost stories that it spawned. Just sitting in your house, and then you faintly hear a man speaking German...
  - bschwindHN 11y ago
    It's weird seeing people on reddit who grew up in the same town as you, but it's even weirder seeing it on Hacker News for some reason. I never heard the broadcasts through metal objects in the house either, but maybe they scaled back the power in the time I grew up there. Never heard any VoA broadcasts either.
caf 11y ago
It's definitely not an urban legend - I witnessed this first hand at a high school friend's house, where headphones attached through long extension cables across the room would pick up the nearby AM transmitter.
plorg 11y ago
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.
- rcxdude 11y ago
  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.
  - gpvos 11y ago
    He was talking about FM, not AM. Which makes it rather weird, as you actually need more of a circuit to decode it.
- david-given 11y ago
  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.
- eitally 11y ago
  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.

luxflux 11y ago

There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Reminds me of a Gilligan's Island episode, Hi Fi Gilligan: https://www.youtube.com/watch?v=3x1XHv0sxro https://www.youtube.com/watch?v=3x1XHv0sxro

thwarted 11y ago
Lucille Ball talking about picking up radio signals in her fillings. https://vimeo.com/72473069 https://vimeo.com/72473069

paulgerhardt 11y ago

That was one specific station - the infamous WLW / W8XO - the first and only US station authorized to operate at 500kW of power.[1] To give you an idea of how powerful that is, take a look at their coverage map: http://i.imgur.com/Aigz1Zh.jpg http://i.imgur.com/Aigz1Zh.jpg The back story is kind of interesting. It was run by Powel Crosley - a sort of 1930's version of Elon Musk. Advertising revenues from the station were so successful he applied to increase the limit from 500kW to 750kW(!). It's a big deal in the ham community, but I only learnt latter that while US stations were limited to 50kW - other parts of the world didn't have such restrictions. Parts of the Middle East have 2,000kW stations. [2] You can get a full download on the Crosley WLW station in this video: https://www.youtube.com/watch?v=CbHjcwIoTiY https://www.youtube.com/watch?v=CbHjcwIoTiY [1] http://www.ominous-valve.com/wlw.html http://www.ominous-valve.com/wlw.html [2] https://en.wikipedia.org/wiki/Transmitter_Solt https://en.wikipedia.org/wiki/Transmitter_Solt

dnet 11y ago
Actually, Solt is not Middle East, but in Central Europe. (I live ~50 km from it.) But yes, it's 2 MW, and at night, it can be heard using conventional receivers as far as Belgium.
- paulgerhardt 11y ago
  Corrected link: http://www.engineeringradio.us/blog/2012/12/the-continental-d323c-medium-wave-transmitter/ http://www.engineeringradio.us/blog/2012/12/the-continental-...
gambiting 11y ago
Well, the Warsaw Radio Tower used to be the tallest man-made structure in the world until it collapsed due to a guy rope failure - and it had a 2 megawatt transmitter, it could be received literally anywhere in the world: https://en.wikipedia.org/wiki/Warsaw_radio_mast https://en.wikipedia.org/wiki/Warsaw_radio_mast
michael_h 11y ago
I grew up about 5 miles from that antenna. I can't say I ever heard the radio through the wiring in my house. The Voice of America antenna array down the street though? I could hear it clearly through my stereo speakers when everything was turned off. It's been dismantled, but I can imagine the number of ghost stories that it spawned. Just sitting in your house, and then you faintly hear a man speaking German...
- bschwindHN 11y ago
  It's weird seeing people on reddit who grew up in the same town as you, but it's even weirder seeing it on Hacker News for some reason. I never heard the broadcasts through metal objects in the house either, but maybe they scaled back the power in the time I grew up there. Never heard any VoA broadcasts either.

caf 11y ago

It's definitely not an urban legend - I witnessed this first hand at a high school friend's house, where headphones attached through long extension cables across the room would pick up the nearby AM transmitter.

plorg 11y ago

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.

rcxdude 11y ago
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.
- gpvos 11y ago
  He was talking about FM, not AM. Which makes it rather weird, as you actually need more of a circuit to decode it.
david-given 11y ago
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.
eitally 11y ago
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.