engineering question #2775



Roman Tanisis, a 32 year old male from Surrey, BC asks on May 23, 2005,

Q:

I have an FM transmitter for my iPod. I find that when my hand is within 5 centimetres proximity to the transmitter or physically in contact, the background hiss is slightly reduced and the signal actually sounds clearer than when I am distant from it. I've also found that when I am touching my stereo antennae I can pick up frequencies with more clarity than when I am not touching it. Another example is that the range of my car's alarm transmitter seems to be significantly increased when I touch the transmitter to my body and point in the direction of my car. What's happening? How is it that my body is amplifying radio frequencies and what exactly is going on?

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the answer

Rodney Vaughan, Engineering Science professor, Simon Fraser University, BC answered on May 23, 2005, A:

The human body is acting as an antenna here. This trick is used with radio pagers where the antenna in the pager is designed to couple to the human body which in turn radiates more efficiently than the pager antenna alone. The same trick cannot normally be used with cellphones, etc., because these work at a different frequency. For most cellphone situations, the human body decreases the efficieny of the radiation. For the FM frequencies of your iPod it works as an antenna.

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