Hi,
There is a chance that at very high train speeds in OO and O gauge that the UID from a NTAG213/215/216 tag may not be read due to the way the tags communicate with RFID modules.
The design of the experimental MERG CANRC522 does not seem to suffer from this problem up to 120 scale MPH in N, OO and O (it reads/writes 4 bytes from I think the first 4 bytes of user EEPROM on the tag).
RFID modules with long antennas may give better performance with trains at high speeds as the tag may be in the communication zone for longer. However there is a trade off as longer antennas could cause problems with interference from tags on other vehicles in the same train. There is a very large model railway using long antennas on their RFID modules but they run their wagons as groups of three with one tag on the middle wagon so the length of the antenna is less of a problem.
Longer tags may also help at higher train speeds but at the moment there are limited shapes and sizes of ready to buy 13.56Mhz RFID tags. Again interference with tags on train vehicles in front and behind may be a problem.
PS The 125khz tags used by the MERG 'first generation' RFID have a 5 byte UID.
Regards
Nick (helping in MERG with research and testing low cost, reliable future RFID solutions for model railways)
