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Don't try this at home
January 11, 2013 12:37 AM   Subscribe

How to listen to the radio with plants (and other objects)
posted by dunkadunc (8 comments total) 12 users marked this as a favorite

 
This plant is in Russian. Would you like to translate? Nope.
posted by mannequito at 12:44 AM on January 11, 2013


The plants speak Russian, but the cables speak British English.
posted by dunkadunc at 12:53 AM on January 11, 2013 [1 favorite]


Right, note to self, don't show the kids.
posted by From Bklyn at 1:10 AM on January 11, 2013


Cool RF burn he got there in the first video. That's gonna hurt for months

This is one of those tricks that broadcast techs have traditionally performed for newbies and visitors. I had it shown to me as an apprentice, & I showed it to trainees many years later.

You can could do a similar trick with a fluorescent tube held near the output tank circuit; it lights up in your hand and if you're clever you can demodulate the RF into audio with it. Can't really do that with modern digital transmitters :(

posted by Pinback at 2:18 AM on January 11, 2013


Just because you can't see it, that doesn't mean it isn't there.

Outdoor exhibitions of residual rf/em fields, as conducted with fluorescent lamps.
posted by Smart Dalek at 2:18 AM on January 11, 2013


Are there any health risks associated with residual rf/em fields like in Smart Dalek's example?
posted by absolutelynot at 4:15 AM on January 11, 2013


The phenomenon is discussed in more detail here, and this long, kind of technical page contains the following description of the days when FCC regulations weren't so stringent:
There were folk tales, probably accurate, of talking rain gutters, sparking fences, singing water pipes, and nearby street lights dimming on modulation peaks.
Unfortunately it seems this only happens with AM transmitters, so if you tried that here in the US you'd just end up getting burned listening to Rush Limbaugh and Michael Savage.
posted by TedW at 4:27 AM on January 11, 2013 [1 favorite]


That's exactly right.

Detection (conversion a radio wave back to an audio signal) of an Amplitude Modulated (AM) radio signal can be as simple as cutting the received signal in half (ie. passing just the posititive or negative half of the received radio wave forward) with a rectifier (aka diode) and passing the remaining part to an "electromechanical transducer."

Rectifiers practically occur in nature ... any time an electric current flows a little easier in one direction than in the reverse direction (eg. a bit of oxidation between two metal pieces of different sizes / shapes), you have a rectifier. If some of the rectified energy is dissipated by, eg., an air gap arc, you also get an electroacoustic transducer in the bargain.

FM detection is much more complex, and beyond the scope of a MetaFilter post.
posted by ZenMasterThis at 6:08 PM on January 11, 2013


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