3 ms·

For anyone wondering how you could pull enough energy out of thin air to get one of these to produce sound... my Dad and I just toured a 50kW clear channel AM r

For anyone wondering how you could pull enough energy out of thin air to get one of these to produce sound... my Dad and I just toured a 50kW clear channel AM radio transmitter site outside St. Louis[1], and it makes more sense when you see how much power is being pumped into that tower! The coils that tune the tower vibrate enough from the RF they reproduce the sound too. Some people don't even need the coil to get sound if you're near enough to an AM tower—you can sometimes hear the signal in certain metal objects. [1] https://www.jeffgeerling.com/blog/2023/mighty-mox-50kw-am-tower-site-tour https://www.jeffgeerling.com/blog/2023/mighty-mox-50kw-am-to...

deleted 3y ago
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15457345234 3y ago
> certain metal objects If I remember correctly it isn't the metal object itself that receives the AM radio, there has to be a diode. In practical terms, dissimilar material junctions - where one is a semiconductor and the other a conductor - form a crude diode. Mercury-amalgam fillings in teeth (with the tooth being the semiconductor) are the apocryphal 'accidental AM radio receiver.'
EvanAnderson 3y ago
My great grandfather (born 1900) related stories about receiving AM 700 in fence wire and a brass bed frame. I was too young to ask questions, but I bet he was talking about the 1930s when it was transmitting at 500,000 (!!!) watts. The family farm was about 40 miles from the transmitter.
- geerlingguy 3y ago
  There's a fascinating tour of WLW on YouTube, too...[1] back when radio was the cutting edge and all the young engineers would go balls to the wall with RF. [1] https://www.youtube.com/watch?v=CbHjcwIoTiY https://www.youtube.com/watch?v=CbHjcwIoTiY
zer00eyz 3y ago
The power of AM radio is interesting. The best example I know of is this: https://www.youtube.com/watch?v=uo9nGzIzSPw https://www.youtube.com/watch?v=uo9nGzIzSPw
MichaelRo 3y ago
As always, crazy Russians. Listening to radio with grass detector: https://www.youtube.com/watch?v=b9UO9tn4MpI https://www.youtube.com/watch?v=b9UO9tn4MpI
- ravenstine 3y ago
  Hah, that is such a late 2000s style video! I love it. That's genuinely interesting but also kind of frightening at the same time. I'm not sure this effect makes total sense to me, though. Normally, a radio signal is a single (center) frequency that is modulated by either amplitude or frequency shift. How can the sound coming from the arcing between the antenna and the grass be that clear at certain points in the video? If it were FM, I'd expect to hear mostly arcing and some faint audio signal a side effect of constant arcing, so maybe it's using AM? Maybe I'm just trying to find a reason to not believe what I saw.
mikewarot 3y ago
I watched that video... it was awesome! Thanks for putting it out there.
- scrumper 3y ago
  I enjoyed it a lot too: https://www.youtube.com/watch?v=Aax-ehkRTnQ https://www.youtube.com/watch?v=Aax-ehkRTnQ Coincidentally I didn't search for it, I was watching a video on how to use FFT on my oscilloscope and I noticed the name "Geerling" on one of the recommended videos on the right hand side and it was this one! And purely a coincidence too, I don't see how YT could have known I was reading this thread.

deleted 3y ago

[deleted]

15457345234 3y ago

> certain metal objects If I remember correctly it isn't the metal object itself that receives the AM radio, there has to be a diode. In practical terms, dissimilar material junctions - where one is a semiconductor and the other a conductor - form a crude diode. Mercury-amalgam fillings in teeth (with the tooth being the semiconductor) are the apocryphal 'accidental AM radio receiver.'

EvanAnderson 3y ago

My great grandfather (born 1900) related stories about receiving AM 700 in fence wire and a brass bed frame. I was too young to ask questions, but I bet he was talking about the 1930s when it was transmitting at 500,000 (!!!) watts. The family farm was about 40 miles from the transmitter.

geerlingguy 3y ago
There's a fascinating tour of WLW on YouTube, too...[1] back when radio was the cutting edge and all the young engineers would go balls to the wall with RF. [1] https://www.youtube.com/watch?v=CbHjcwIoTiY https://www.youtube.com/watch?v=CbHjcwIoTiY

zer00eyz 3y ago

The power of AM radio is interesting. The best example I know of is this: https://www.youtube.com/watch?v=uo9nGzIzSPw https://www.youtube.com/watch?v=uo9nGzIzSPw

MichaelRo 3y ago

As always, crazy Russians. Listening to radio with grass detector: https://www.youtube.com/watch?v=b9UO9tn4MpI https://www.youtube.com/watch?v=b9UO9tn4MpI

ravenstine 3y ago
Hah, that is such a late 2000s style video! I love it. That's genuinely interesting but also kind of frightening at the same time. I'm not sure this effect makes total sense to me, though. Normally, a radio signal is a single (center) frequency that is modulated by either amplitude or frequency shift. How can the sound coming from the arcing between the antenna and the grass be that clear at certain points in the video? If it were FM, I'd expect to hear mostly arcing and some faint audio signal a side effect of constant arcing, so maybe it's using AM? Maybe I'm just trying to find a reason to not believe what I saw.

mikewarot 3y ago

I watched that video... it was awesome! Thanks for putting it out there.

scrumper 3y ago
I enjoyed it a lot too: https://www.youtube.com/watch?v=Aax-ehkRTnQ https://www.youtube.com/watch?v=Aax-ehkRTnQ Coincidentally I didn't search for it, I was watching a video on how to use FFT on my oscilloscope and I noticed the name "Geerling" on one of the recommended videos on the right hand side and it was this one! And purely a coincidence too, I don't see how YT could have known I was reading this thread.