A removable spindle for use in a thermal transfer printer houses dual RFID reader antennas that are used to read an RFID tag attached to the core of the print media. The information provided by the RFID tag enables the printer to self-calibrate based on the type of media loaded. The antenna design eliminates “null” areas at which the tag cannot be read, and enables the tag to be read around and across the entire length of the printer spindle. The design also allows the media holder to be easily removed from the printer.