Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Radio Transmission

  1. Aug 17, 2005 #1
    can anyone explain to me why radio reception/tv reception ect.. come in more clearly when i hold the antenna?
    i am assuming my body is acting as a better receiver
    but can someone actually explain why?
    thank you
    shawn small
  2. jcsd
  3. Aug 17, 2005 #2
    I noticed that to when I lived in Bosnia and had to move antennas for the TV so that picture is better. As soon as I would touch the antenna picture would get much better.
  4. Aug 17, 2005 #3


    User Avatar
    Gold Member

    Although I don't really know anything about the specifics, I believe that your bioelectric output alters the capacitance of the aerial. Proximity alarm systems such as for cars operate on that principle. If you notice, you can be close to the aerial without actually touching it and still have an effect.
  5. Aug 17, 2005 #4
    This is close, but it't not the bioelectric output- its just the capacitance
    and inductance. A bag of seawater the size and shape of a person
    would have the same effect on the TV reception.

    Basically, you are either 1) enlarging the size of the antenna by
    grabbing it or 2) you are improving the coupling between the receiver
    and the antenna's connection. This second effect would be called
    impedance matching where the first effect would be called "increasing
    the effective aperture of the antenna".
  6. Aug 17, 2005 #5


    User Avatar
    Gold Member

    Thanks for that clarification. I never knew what caused body capacitance, so just assumed that it had to do with cellular electrical activity. I suppose then that sticking a piece of tinfoil or a coathanger on it works for the same reason rather than just from changing the shape of the antenna?
  7. Aug 17, 2005 #6

    If you define a pair of electrical terminals, then the configuration of the whole
    universe affects the capacitance measured between them. Of course the
    more distant objects will have a very small effect.

    Capacitance is measured in Farads where [tex] C = Q/V

    What this says is that if I charge my terminals up to one volt, the
    capacitance is a measure of how much charge it took to do it.

    A large capacitor can take a large amount of charge before the
    terminals get up to one volt. Originally when voltage was thought
    to be a form of pressure, capacitance was thought to be like
    the "size" or capacity of a storage tank.

    A fat, wide tank will take a lot of water before the pressure is high.
    This is like a large capacitor.

    A tall narrow tank will build pressure quickly with only a little water.
    This is like a small capacitor.
    Last edited: Aug 17, 2005
  8. Aug 18, 2005 #7
    so is it the water in the human body that makes it such a good antenna?
  9. Aug 18, 2005 #8
    No. Salt water or water is not a good antenna material.

    It's just that the body may help receive a signal from a small antenna
    under the right conditions. Usually the body interferes with the
    action of a well-designed antenna.

    I only refer to water above to help explain capacitance.
  10. Aug 18, 2005 #9


    User Avatar
    Gold Member

    Thanks. That clears up a lot of misconceptions that I had.
  11. Aug 18, 2005 #10
    thanks for the clarification
    is it something specific about the human body that aides the antenna specifically?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook