The European Radio Astronomy Club frequencies, the ionosphere is opaque. Here, two targets are possible: the Sun with its solar flares or Jupiter, which is also a very strong radio source, together with the moon Io, which is a very powerful natural radio wave transmitter. When Jupiter, Io and the Earth are aligned, it is possible to hear this radio source very clearly. The European Radio Astronomy Club The European Radio Astronomy club (ERAC) is Europe's only group coordinating the work of radio astronomers to jointly use radio waves to study the universe at radio wavelengths. It was founded in 1995 by Peter Wright, who
Radio propagation propagation. The interference between the direct beam line-of-sight and the ground reflected beam often leads to an effective inverse-fourth-power (1/distance) law for ground-plane limited radiation. Lower frequency (between 30 and 3,000 kHz) vertically polarized radio waves can travel as surface waves following the contour of the Earth; this is called "groundwave" propagation. In this mode the radio wave propagates by interacting with the conductive surface of the Earth. The wave "clings" to the surface and thus follows the curvature of the Earth, so groundwaves can travel over mountains and beyond the horizon. Ground waves propagate in vertical polarization so vertical