Antenna size for decent read range on an xNT?

edited November 2016 in RFID/NFC
I'm working on making a setup to lock/unlock my car doors with my xNT, however, I have yet to find an antenna that will read it from anywhere but touching it. I'm using a keyduino for this project, and even the giant credit card sized antenna will only pick it up when I'm dead on it, and in a corner of the coil. Anyone else have this issue?

Im thinking about just getting a custom pcb printed with a coil on it, but it is going to take a lot of research to figure out exactly how big I can make it without interfering with the actual data transmission.


  • It's not only the size of your reader antenna, but also the size of your tag antenna. Later one is limited by the fact that the tag itself is tiny. Plus the entire technology is working with near-field so it's not designed to have a big reader range. Bigger reading distances not only require careful antenna design but also powerful electronics (as in literally powerful, they are quite demanding in terms of power demand). My guesstimate would be you can't get more than maybe 20 or 30cm with a single-digit watt base station. The new flexible tags which have been around on the forum should give you quite a bit of extra range compared to glass capsules. For glass capsules I'd say 3 to 5 cm would already be good. You can build an antenna to properly guide the magnetic field from one end of the glass tag to the other. They'd look more like a coil around some magnetically conductive core that's U-shaped (with the glass tag closing the U shape to an O.
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