A comparison of loop antennas

The author compares some of the loop antennas currently used for radiated emissions testing per VDE. It is shown that field strength readings in a uniform field correlate between antennas of different design. However, field strength readings in a nonuniform field may vary by as much as 16.9 dB from one loop design to another. Several loop antennas are compared, one of which is used in two different configurations including a passive loop with ten frequency bands; a battery operated active loop; an active loop that requires an external power supply and has a metal tripod to accommodate its power and output cables; and the active loop antenna in which a nonreflecting base is used in place of the manufacturer´s metal tripod. Each loop covers the frequency range of 9 kHz to 30 MHz. It is concluded that, to achieve the most accurate EMC (electromagnetic compatibility) measurements possible, loop antennas should be calibrated in uniform magnetic fields only