The ETS-Lindgren 7604 Shielded Coil Antenna is a magnetic field pick-up coil 13.3 cm (5.25 in) diameter, and has a loop that is constructed of aluminum. The loop has 36 turns of 7 x 41 Litz wire for lower inductance. The 7604 can be individually calibrated in accordance with the IEEE-291 Section 2.3.1 methods, using NIST traceable equipment. By knowing the actual antenna factors and performance characteristics of an antenna instead of typical data, you can more accurately measure field strength in your tests.
ETS-Lindgren (EMCO) 7604 Specs