Measurements process of vertically polarized electromagnetic surface-waves over a calm sea in the HF band over a spherical earth

A HF surface-wave experimentation across a 220 km sea water path is carried out at 5, 10, and 20 MHz in order to evaluate the relative field strength attenuation with distance and beyond the horizon with a low measurement uncertainty. Although the theories are well known, the experimentation is described from the transmitter's implementation until the RF equipment in order to improve the signal to noise ratio. The measurement setup described proves the reliability of the data.