Open field range calibration at HF and VHF

Calculated results obtained using the FCC Bulletin OST 55 site-attenuation equation are compared to those of a more rigorous model developed by A.A. Smith et al. (1982), and measured site attenuation is also compared to the model results. The OST 55 model leads to significant errors because of its neglect of the phase difference in the direct and indirect paths between the transmitting and receiving antennas and of antenna-to-antenna and antenna-to-image coupling. The measurement data confirm and supplement the results of Smith et al. The data show that it is possible to obtain better than 2 dB correlation between measurements with polarized dipoles and their model even in the range of 25-80 MHz. Repeatability of the measurements among three different ranges has been verified