Pencil Beam Radar for Ionospheric Research

A high frequency pencil beam radar for ionospheric research has been in operation for some time on Bribie Island near Brisbane, Australia. The beam is formed as the product of the polar patterns of a 1 km arm used for transmitting and another 1 km arm at right angles for receiving, the whole array forming a 1 × 1 km cross. The effective beam is about 4° wide at 4 MHz. Each polar pattern is able to have its peak shifted up to 20° off vertical (at 4 MHz) using digital phase shifting. Each of ten transmitting aerials is a spread dipole and each of ten receiving aerials is a crossed delta with 90° phase shifters between the two arms. The radar operates on frequencies near 2, 4 and 6 MHz, using ordinary or extraordinary rays as desired.