[NetBehaviour] Lightning-Produced Radiation Suppressing Shortwave Radio Reception

[Alan Sondheim]

Lightning-Produced Radiation Suppressing Shortwave Radio Reception

http://www.alansondheim.org/setup.jpg
http://www.alansondheim.org/weather.png
http://www.alansondheim.org/setup2.jpg
http://www.alansondheim.org/silentdrive2.mp4
http://www.alansondheim.org/silentdrive1.jpg
http://www.alansondheim.org/silentdrive2.jpg

Recorded in Aurora, Colorado, across from a reservoir.

The weather was terrible - see weather.png in the area, but Aurora
was somewhat spared.* I was curious how lightning would interact
with shortwave beyond the usual static, so I set up three things -
an analog shortwave radio (with somewhat broad tuning) using both 2
MHz and 3.8 MHz; a Zoom H2n to record both the radio and thunder;
and a Panasonic camera to record video including both the lightning
strokes and the radio. To my surprise, I found after some of the
strokes, that the radio reception decreased immediately - it then
returned on a characteristic curve. In other words, there was a
very short moment of silence beginning with the stroke. For the
setup, see setup.jpg and setup2.jpg. For the image of the sound
amplitude, see silentdrive1.jpg. For the image of the spectrum, see
silentdrive2.jpg; the bluish area to the right of the large
rectangle is the reception of some emission that blanked the sound,
which then recovered (note the slope on the right). For the video,
see silentdrive2.mp4. The effect is small, but it's there. It's
almost unnoticeable. It stems from the radio, not the Panasonic
video recording, since it was audible in the environment. It's
amazing to hear a phenomenon for the first time; I've listened to
shortwave all my life, as well as very low frequency radio more
recently. But I never heard this effect before. Note that it didn't
occur with every lightning stroke, but when it did, it was clear
and euphoric. I did attempt to find some explanation online, but
failed. The radio by the way was an inexpensive Tecsun, with poor
signal differentiation. What I love about it is that, as well as
the analog reception - it can pick up more anomalies without
digitization, and the smooth tuning makes a path for experimenting
with symptoms like these.

*There was flooding in Denver.