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total noob here. I have a general question regarding the NFC tags:

I have a 12mmx19mm NFC tag. I notice I was able detect it (1-1.5cm away) without a problem until I place a circuit board behind it (or close to it). Is this a common issue?

Would having a larger NFC tag help? Or anyway for the NFC to work in front of a circuit board? Thanks!

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Antennas of NFC tags are typically made of coils with one or more windings. When current flows through the coil, it generates a field that goes through the center perpendicular to the coil surface.

If you put anything conductive (like a circuit board) behind or in front of that coil, it will prevent the magnetic field going through the coil. This reduces the reading distance of the NFC tag.

One thing that could help is a thin sheet of ferrite between the circuit board and the coil. This will restore the magnetic field to some amount.

A larger NFC tag could help, but in most cases it will not, because larger coils have weaker magnetic fields.

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