I’ve noticed that often when watching broadcast television (that is, from the antenna, not cable), the quality of the reception will depend on where I’m standing. Is the human body capable of modifying EM transmissions? Also, I’ve noticed that the quality of playback of tapes that I have already recorded will depend on where my antennas are placed. Any ideas why this could be?
As Sublight said that Cecil said, yes you can act as an antenna. And sometimes parts of you can act as a detector. People have been known to receive and detect radio signals when near an AM transmitter antenna. Non-linear electrical conduction in tooth fillings detects the modulation and they hear the audio through bone conduction.
One quick note: “mailbag” links are not written by Unca Cece – Sublight’s link was instead written by one “SDSTAFF Tech”. However, Cecil did write a column about radio reception by dental work, Is it possible to hear radio broadcasts through your teeth?, which is included in his third opus, Return of the Straight Dope.
Adding to what others have said, there are at least two possible ways for the human body to affect reception. The first is when you touch or stand close to the antenna, and your “body capacity” changes the antenna characteristics. However, there is a second case when you are standing farther away, and your body can reflects the signals – particularly in the case of the shorter wavelengths used by FM and TV. Thus, standing in different parts of the room can hurt or help reception. Similarly, overflying airplanes and even trees can have an effect. The shorter the wavelength the more visible the impact. I particularly notice it on weak UHF TV signals during windy days, since I am located near numerous trees which sway in the wind.
You might find the following from the 1922 Radio Boys Trailing a Voice interesting: