Read Range and Performance Expectation

Please note that this is an extract graciously provided by the manufacturer, Amal Graafstra at Dangerous Things.
 

Passive RFID and NFC tags are magnetically coupled devices that power themselves and communicate data over a shared magnetic field the reader generates. This means their effective read range and performance depends entirely on how well the antenna coils of both the tag and reader couple with each other. This typically means the shape, size, and orientation of both antennas must be complimentary.

Unfortunately, most reader devices, including mobile phones, typically have antennas designed with thin PCB traces made into blocky rectangular shapes that lay along a flat plane. These antenna designs are great for coupling with and reading large flat label tags, credit card style tags, and access cards which also share this antenna shape, but they have a hard time coupling to the very small cylindrical antenna coil inside our x-series tags. Most mobile phones and reader devices have a “sweet spot” or two that must be located and used each time to get consistent results. Other devices, such as the Samsung Ezon electronic deadbolt lock, sometimes use wire wound coil antenna loops inside, which work much more reliably with small glass tags like our x-series tags. You should not expect your USB reader or mobile device to achieve the same read range with our x-series tags that you normally get with a label tag or card style tag. Here are some example videos detailing typical read performance and how to find that “sweet spot”.