LF Antenna Construction (125 to 134 kHz)

Discussion in 'Wireless & RF Design' started by mossman, Apr 8, 2013.

  1. mossman

    Thread Starter Member

    Aug 26, 2010
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    I am attempting to capture the radiated wave from a couple passive RFID tags, one which transmits at 125 kHz and the other at 134 kHz. I need to make a rudimentary AM antenna to detect these signals and view the modulation on an oscilloscope. I am currently using a signal generator and near field antenna probe to transmit a carrier to stimulate, bias, etc. the tag which takes the signal, modulates it, and re-transmits it. I need to capture this re-transmitted modulated signal and view it on a scope so I can decode the modulation. Any help would be greatly appreciated.
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Are you serious about the frequency? It seems way to low to be practical. I say that because an efficient antenna at those frequencies is incredibly long and there is very little bandwidth for data transmission at those frequencies. Very slow CW on a waterfall display is about all you can manage.
     
  3. davebee

    Well-Known Member

    Oct 22, 2008
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    A plain old ferrite loopstick should work.

    I used to pick up LORAN transmissions at 100 kHz when working on circuits at my house. Even though the LORAN transmitters were several hundred miles away, it still was sometimes a struggle to keep the LORAN signal out of my breadboarded circuits. A few inches of wire at the input of an op-amp would pick up enough 100 kHz energy to show up on my scope.
     
  4. Papabravo

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    Feb 24, 2006
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    Last edited: Apr 8, 2013
  5. davebee

    Well-Known Member

    Oct 22, 2008
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  6. Papabravo

    Expert

    Feb 24, 2006
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    Still no info on the available bandwidth utilized and how the messages are encoded and decoded.
     
  7. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Maybe the scope does not need it to show the signal... I guess.
     
  8. mossman

    Thread Starter Member

    Aug 26, 2010
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    There's a ferrite stick antenna in a cheap AM/FM radio I have at home. Would this be able to pick up the transmitted RFID signal? Would I need to remove some of the loops to tune it to the 134 kHz range?
     
  9. bertus

    Administrator

    Apr 5, 2008
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