3 ms·

I'm unable to look it up right now, but there is an excellent video of a man touching a long grass stalk to (what I presume) is an AM radio tower. The grass bur

I'm unable to look it up right now, but there is an excellent video of a man touching a long grass stalk to (what I presume) is an AM radio tower. The grass burns, and in the sizzling you can hear the radio station. In principle, I think it's approximately the same theory of operation as the razor blade diode -- which is also similar to a "Cat's Whisker".

marcodiego 5y ago
This: https://www.dailymail.co.uk/sciencetech/article-3276974/Incredible-video-shows-foolhardy-Ukrainians-listening-radio-just-touching-WEEDS-against-50-000-watt-transmitter-station.html https://www.dailymail.co.uk/sciencetech/article-3276974/Incr... Beware: RF burns take unusually long to heal. Also, the leaves are not working as the detector, they're an extremely inefficient speaker.
- bjt2n3904 5y ago
  No, I think they actually are working as a detector, just a mechanical one! The movement of the grass (relative to the surface of the tower) is not sinusoidal, it's clipped just like a diode rectifier -- and the grass' springiness acts like a mechanical capacitor, smoothing the motion out.
  - marcodiego 5y ago
    Interesting theory, but I'm still unconvinced. AFAIK, the electric potential of the tower is a product of the signal that is being sent multiplied by the carrier wave. When the potential on the tower is high, it will burn the weed stronger; when the potential of the tower is close to 0, the rate of burn of the weed will not change. The burning weed will reproduce the potential of the tower: signal times carrier. Since the carrier is too high a frequency for our ears or the weed too, we only listen signal that is inside human hearing interval.
    - bjt2n3904 5y ago
      I think not only is the carrier too high for our ears to hear, but also too high for the grass to vibrate at. (500-800 kHz is pretty fast, Hence, the mechanical damping!) I think I'm pretty close, but I need Smarter Every Day on this one!

marcodiego 5y ago

This: https://www.dailymail.co.uk/sciencetech/article-3276974/Incredible-video-shows-foolhardy-Ukrainians-listening-radio-just-touching-WEEDS-against-50-000-watt-transmitter-station.html https://www.dailymail.co.uk/sciencetech/article-3276974/Incr... Beware: RF burns take unusually long to heal. Also, the leaves are not working as the detector, they're an extremely inefficient speaker.

bjt2n3904 5y ago
No, I think they actually are working as a detector, just a mechanical one! The movement of the grass (relative to the surface of the tower) is not sinusoidal, it's clipped just like a diode rectifier -- and the grass' springiness acts like a mechanical capacitor, smoothing the motion out.
- marcodiego 5y ago
  Interesting theory, but I'm still unconvinced. AFAIK, the electric potential of the tower is a product of the signal that is being sent multiplied by the carrier wave. When the potential on the tower is high, it will burn the weed stronger; when the potential of the tower is close to 0, the rate of burn of the weed will not change. The burning weed will reproduce the potential of the tower: signal times carrier. Since the carrier is too high a frequency for our ears or the weed too, we only listen signal that is inside human hearing interval.
  - bjt2n3904 5y ago
    I think not only is the carrier too high for our ears to hear, but also too high for the grass to vibrate at. (500-800 kHz is pretty fast, Hence, the mechanical damping!) I think I'm pretty close, but I need Smarter Every Day on this one!