Measurements of antenna characteristics above different conducting planes

Antenna measurements by the three-antenna method at five different types of open-area test site (OATS) are reported. The measurement repeatability of site insertion losses (SIL) and antenna factors (AF) of tuned dipole antennas are discussed in this paper. Deviations of measured SIL with a pair of tuned dipole antennas are shown in comparison with the predicted ones. The predicted SIL is calculated by combining the measured S-parameters of the balun and the impedance matrix of the antenna elements. The results of SIL measurement at four frequencies are distributed around the predicted ones. SILs measured at 24 frequencies with a pair of tuned dipoles were provided by the National Physical Laboratory (NPL) and we measured SILs under the same conditions as at NPL. The results are shown in comparison with the predicted SILs. The differences in the SILs measured by the two laboratories were within ±0.4 dB from the predicted SILs over the frequency range 30 MHz to 1000 MHz. For the case of AF, the results obtained show that the repeatability of the AF for a tuned dipole antenna is within ±0.3 dB when measured at the same height above a conducting plane