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 M_Hz (~ 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 (O mode) or left (X mode) circular polarized radiated beams, are described. The heater is powered by two 1500-horsepower diesel electric gene{ators. It can be operated throughout the year over -30øC to 40 C ambient temperature extremes. Future improvements include the construction of an even larger 840 x 840 m (24 x 24 antenna) array with a gain of 37.5 dBi.

The Department of Commerce's Platteville transmitter facility has been used to modify the ionosphere since 1970. Design concepts and a description of major components at the facility are discussed. When used for ionospheric modification studies, one of two 10‐element ring‐array antennas, each producing right‐ or left‐handed circularly polarized signals, is excited by a transmitter which develops up to 2 Mw of average power. These arrays permit operation in the frequency range from 2.7 to 10 MHz, as required to approximately match varying ionospheric critical frequencies.

The purpose of this paper is to describe the results of experiments undertaken to assess the potential impact of the operation of the Satellite Power System on the D and E regions of the ionosphere, and on telecommunication systems that are dependent upon the structure of the lower ionosphere. Using the high‐power, high‐frequency transmitter facility located at Platteville, Colorado, power densities equivalent to the Satellite Power System can be delivered to heights of 70 to 100 km above the surface of the earth. Observations of the performance of telecommunication systems that operate in the VLF, LF, and MF portions of the spectrum have been investigated during times when the ionosphere was modified with power densities comparable to the Satellite Power System and when it was not. The results obtained indicate that the Satellite Power System as currently designed with a peak power density of 23 mW/cm2 is not likely to impact in an adverse manner upon the performance of VLF, LF, and MF telecommunication systems.

No abstract

No abstract