Eight spaced antennas were used to receive 250-MHz signals from quasi-geostationary polar beacon satellites. The system was deployed in such a way as to intercept the ionospheric volume illuminated by the European incoherent scatter (EISCAT) high-power HF heating facility near Troms¿, Norway (69.6 ¿N, 19.2 ¿E). The spaced-receiver analysis was then used to investigate the relationship between the elongation, the characteristic velocity, and the intensity of irregularities generated by the heater. The results were also compared with those from natural irregularities. It was observed that the elongation of both classes of irregularities increased with their intensity. During daytime heating experiments the axial ratios of controlled heater-generated irregularities were found to be a factor of 2 larger than the background natural irregularities. On the other hand, the characteristic velocity of artificial irregularities decreased with their intensity.¿ 1997 American Geophysical Union