Radio interference and the Human Body.

[Sarpedon]

I noticed a curious phenomenon this morning. As my radio played my morning alarm music, and I got up to get dressed, when I sat in a particular place and leaned forward to reach inside my sock drawer, there was suddenly a great burst of static on the radio. I was about five feet from the radio, and not touching it or anything metal at all. When I leaned back it subsided. After repeating this a few times, I was able to locate the exact point to put my torso to cause static. It was an FM station, btw.

I had never heard before that something as small as the human body could cause this sort of thing. Does anyone have any insight as to how this happens? Has this happened to anyone else?

 

[barbos]

It happens all the time. Your body does not have to be a conductor to cause interference. Large chunk of dielectric with dielectric permittivity different from 1 will affect radio waves. Water has comparatively huge dielectric permitivitty around 100 (at radio-frequencies)
For comparison, ordinary plastic is usually around 2 or something like that.
Also water in human body is pretty good conductor, cause it contains shitload of different ions.

 

[Sarpedon]

Oh, good, I'm glad I'm not radioactive.

Why that particular spot?

 

[barbos]

Oh, good, I'm glad I'm not radioactive.

Why that particular spot?

No reason, it's just happened to be that particular spot which cause signal to fade.
your body acts like an antenna which reradiates incoming waves with different phase from origin and then it's just geometry and calculation of how these two different waves superimpose at the receiving antenna.

 

[thebeave]

yep, what barbos said. Those of us who are children of the 1960's and '70's have many memories of having to stand perfectly still next to the TV rabbit ears while dad watches the news for half and hour. ugh. My legs get tingly just thinking about it.

 

[Sarpedon]

while I certainly knew that if one were actually touching the antenna that would have an effect, I didn't know that sitting five feet away, not in contact with anything metal, also could!

 

[barbos]

while I certainly knew that if one were actually touching the antenna that would have an effect, I didn't know that sitting five feet away, not in contact with anything metal, also could!

Light and radio waves are both the same electromagnetic waves. And glass obviously affect light because you can see it bends it and reflects it.
Yet glass is not a conductor.

 

[thebeave]

while I certainly knew that if one were actually touching the antenna that would have an effect, I didn't know that sitting five feet away, not in contact with anything metal, also could!

The radio waves that you receive at your house have been reflected and scattered in multiple directions from the original transmitter. Trees, buildings, mountains, plumbing, chicken wire in the stucco siding and wiring in your house create a huge clusterfuck of chaotic radio waves by the time it reaches your radio. And different frequencies are affected in different ways. That's the reason for much of the interference you hear on your radio or see on your TV. By you standing nearby, you may be reflecting a signal towards your antenna to give you better reception. Or you may be blocking the main signal, giving you worse reception. It can get crazy and very weird.