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intensity of radio em field

Discussion in 'Electronic Basics' started by Alain Henry, Dec 19, 2004.

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  1. Alain Henry

    Alain Henry Guest

    I am planning to buy a home weather station with a remote temperature
    sensor (wireless, ie using radio transmission at 433 MHz).

    I am trying to figure out how the intensity of the electromagnetic
    field we would have indoor caused by this radio emitter would compare to
    that ambient, background, field (caused by radio and TV emitters, cell
    phone relay stations, other electronic equipment, etc.). The manufacturer
    does not give information on the power of the radio emitter (or on the
    exposure we would get fom it).

    World Health Organisation gives a typical value for background exposure to
    such exposure (0,1 W/m2) to radio and TV emitters. What would be the
    exposure for the radio sensor?

    Thanks for any help

  2. Andrew Holme

    Andrew Holme Guest

    Those 433 MHz devices put out milliwatts. TV transmitters run megawatts.
    The field strength falls off as the square of distance. Your additional
    exposure will be orders of magnitude below background.
  3. Alain Henry

    Alain Henry Guest

    Thanks for the info. I'd like to have accurate references and info. Any
    reference I could explore?
  4. Andrew Holme

    Andrew Holme Guest

  5. Alain Henry

    Alain Henry Guest

    Apologies, I was not clear in my previous question. I meant references to
    the specs or a manufacturer of such small radio devices. I'll go
    and search internet anyway. Thanks again.
  6. Rich Grise

    Rich Grise Guest

    Maybe you could check with whoever it was you were planning to buy the
    home weather station from.

    Good Luck!
  7. TaxSrv

    TaxSrv Guest

    If you can't easily find the info, I ran the RF safety calculator on
    an U. of Texas website. At 433MHz, and a distance of 20 feet from the
    antenna, 1,650 watts is the threshold of a safety problem. With a
    sensor broadcasting from the top of your house, no one else living
    within hundreds of miles of you could operate such a device due to
    interference! And it sure couldn't be battery powered....

    Fred F.
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