|MadSci Network: Physics|
Hi Mark, That's a good observation that you made. In general, this is known as proximity effect. There are two possibilities: 1. Your body is shielding or attenuating some of the signal from the radio station 2. Your body is detuning your receiving antenna It's possibly both effects are taking place. I suspect this because you say you live out in the country, in which case you might be far away from the radio transmitter antenna so signal strength is weak. You also mentioned that you use a cheap antenna which is most likely omnidirectional and probably not very well tuned. Radio waves, like visible light, contain both electric and magnetic fields. Your body looks like a large bag of water to radio waves. Water acts as a dielectric, meaning it concentrates electric fields. You might think of it as a lens in visible light. As you move away, you are altering the strength of the electric field in the radio waves, which you notice as varying signal strength. Mobile phones are also affected by the proximity of the human body. Mobile phone manufacturers tune their antennas assuming a human body is close by. Of course, they can't account for all possibly orientations, so they often recommend not touching the antenna during operation as this can reduce it's effectiveness. I hope that helps. http://madhu.com - http://madhu.com/blog
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