High-power radiating facility at the HIPAS observatory

UCLA's radio frequency ionospheric heater, 25 miles (40 km) east of Fairbanks, Alaska, is described. The heater consists of eight crossed dipole antennas arranged in a circular pattern to give a gain of 18.4 dB over isotropic at 2.85 MHz (“ 2nd electron cyclotron harmonic). At 1.2 MW total radiated power the array has a calculated equivalent radiating power of 84 MW. Each antenna is driven by a 150-KW transmitter, originally from the Platteville heater. The eight transmitter antennas are managed by a personal computer which controls power, modulation, and beam steering. Methods of tuning the antennas, to achieve either right (0 mode) or left (X mode) circular polarized radiated beams, are described. The heater is powered by two 1500-horsepower diesel electric generators. It can be operated throughout the year over -30 C to 40 C ambient temperature extremes. Future improvements include the construction of an even larger 840 × 840 m (24 × 24 antenna) array with a gain of 37.5 dBi.