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About Radio Transmitters

Discussion in 'General Electronics Discussion' started by Excelseo, Jan 27, 2015.

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  1. Excelseo

    Excelseo

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    Jan 27, 2015
    I am constructing an RC airplane, along with a radio reciever/transmitter, and I have recently learned that under FCC law, unlicensed transmitters can only transmit with a range of 200 ft. or less. To have a range of 200 ft. and still receive enough power at the edge of the radius, how much power would I need?
     
  2. Gryd3

    Gryd3

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    875
    Jun 25, 2014
    That would depends on a wide array of factors. I am not skilled enough to even ballpark it for you though.

    Any obstructions,
    Weather,
    Frequency,
    Rx Antenna,
    Tx Antenna,
    Noise,

    Perhaps someone can give you a ballpark, but you may end up needing to overcompensate, then dial back the signal to be FCC compliant. Of course, you would also need to determine what an acceptable signal would be at 200 ft. to comply. You can't just stop radio waves at the 200 ft. mark, they will continue well past, but decay as you move away.
     
    davenn likes this.
  3. davenn

    davenn Moderator

    13,557
    1,854
    Sep 5, 2009
    The FCC regulations are more likely to give you a max transmitter power and antenna gain
    this results in a maximum ERP ( Effective Radiated Power) rather than a specific distance
    As Gryd3 rightly said, distance is dependant on ALL those in his list and a few more


    Dave
     
  4. hevans1944

    hevans1944 Hop - AC8NS

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    2,074
    Jun 21, 2012
    Would you please post a link to where it states "under FCC law, unlicensed transmitters can only transmit with a range of 200 ft. or less".

    There is only one band (26 to 27 Mhz) where unlicensed, un-certificated, kit-based RC transmitters are permitted, and then only on six particular crystal-controlled frequencies. See this link.

    You might be better served with a certificated (FCC type-approved) transmitter that uses a higher frequency ISM band. Although these are also unlicensed, they cannot be constructed from kits, must be certificated by the FCC, and no modifications are allowed by the end user. Visit this link and subsequent references to 47 C.F.R. Part 95 Subpart C.
     
  5. Bluejets

    Bluejets

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    824
    Oct 5, 2014

    Attached Files:

  6. Excelseo

    Excelseo

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    Jan 27, 2015
    Never mind. After further review, I have found the limit is a single watt. Apologies for the inconvenience.
     
  7. Bluejets

    Bluejets

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    Oct 5, 2014
    According to what I read it's actually less than 1 milliwatt....

    Low-Power, Non-Licensed Transmitters
    Throughout this bulletin the terms "low-power transmitter," "low-power, non-licensed
    transmitter," and "Part 15 transmitter" all refer to the same thing: a low-power,
    non-licensed transmitter that complies with the regulations in Part 15 of the FCC rules.
    Part 15 transmitters use very little power, most of them less than a milliwatt. They are
    "non-licensed" because their operators are not required to obtain a license from the
    FCC to use them.
    Section 15.1
     
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