Optimal Substrate for Low Frequencies?

Hello all,

I am trying to make a PCB antenna for NFC application @ 13.56 mhz. What would be the best substrate for this application? Is there an online vendor that ships small amounts of such a substrate? I don't need a whole lot.

Thanks in advance.

These low frequency "antennas" are nothing but simple inductors. They are not sensitive to the substrate properties. You can choose whatever makes sense mechanically, or is easy to manufacture.

FR4 is OK, but its Er maybe vary a little, you can make a yield simulation.