short range Rf transmitter

Discussion in 'The Projects Forum' started by hasitha112, Nov 3, 2010.

  1. hasitha112

    Thread Starter New Member

    Nov 3, 2010
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    hey guys i need some help.. @ first sorry for my poor grammer on english...

    what i need to make is a transmitter that can transmit stereo audio signals from my computer.. but its must be short range. (the longest transmitting range is 5-6 meters not above) pls i need help. i tried lot of transmitters but they all transmitting too long. as a law in our country. long distance transmitting is illegal. so thats why i need a short range transmitter that can transmit signals only in my room..
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    The problem is that the "RF gotta go somewhere". To reliably limit the range you can go up in frequency or down in power. Going down in power is relatively straightforward. Going up in frequency is more difficult than you can possibly imagine.
     
  3. marshallf3

    Well-Known Member

    Jul 26, 2010
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    It's not so much the power output of the transmitter as it is the ERP - effective radiated power.

    If you really need to limit how far the signal goes try using less antenna or partially shielding what you have. Replacing the antenna with a simple dummy load may be all you need to do.

    What frequncy band does this operate in, pix, anything else you can add?
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Couldn't you just introduce a variable level of shielding? If you absorb some of the RF energy at the source, range is reduced. I'm picturing a screened cage for the transmitting antenna.

    Actually, detuning the antenna might be another route.

    [update] Hah! Marshall scooped me.
     
  5. Papabravo

    Expert

    Feb 24, 2006
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    Yes, all of that is true. The real problem is how to know for sure what is going on without a boatload of equipment. I get the impression that there is a penalty for guessing incorrectly.
     
  6. DickCappels

    Moderator

    Aug 21, 2008
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  7. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    What an interesting article Dick, thanks.
     
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