Calibration of biconical antennas on a small ground plane

A new way is proposed, and verified by experiment, to measure the free-space antenna factor (Fafs) of biconical antenna over 30 MHz to 300 MHz, by the standard antenna method. The antennas were horizontally polarized above a small (12 m wide) open area test site (OATS). The usual method of calibrating EMC antennas is to place two antennas at a given separation in a horizontal plane. Biconical antennas have a uniform H-plane pattern, making it possible to stack the antennas in a vertical plane. The Fafs measured with the new method is in close agreement (difference less than 0.6 dB) to that with the vertically polarized method from the draft IEC international standard CISPR 16-1-6. Because the antennas are stacked vertically, a smaller ground plane can be used. Because the antennas are horizontally polarized, the vertically routed cable is orthogonal to the antenna so the interaction of cable and antenna is minimized.