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INSTRUCTIONS: BUILD A KEYCHAIN RFID DETECTOR
STEP 1
Start by constructing the radio antenna that will detect the RFID readers' 13.56 megahertz signal.
A
Find the RF Choke and open the package. This is a "ferrite core" wrapped in insulated wire, designed to filter out (or "choke") radio signals for sensitive electronics. Ferrite is a form of iron that is mixed with other material so that it has a high flux density, which gives it special properties that allow it to concentrate radio signals. An antenna wrapped around ferrite will behave like an antenna of much larger size, capturing more radio frequency energy.
B
Cut the silver wires that extend from the ends of the ferrite. Cut the copper wire where it attaches to the stubs of the silver wire, and unravel it, removing it completely.
C
Next, find the length of copper wire that we have supplied. Wrap it around the ferrite so that it forms exactly 17 complete turns. The wire should start at one end of the ferrite, loop around it to the opposite end, then return in one straight line. Leave about 1 inch of extra wire trailing from the ends.
D
You may wish to tape the ends of the antenna so that the wire does not unravel.
Next...
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