Data on 50- and 12-MHz E region coherent echoes from approximately the same directions and in a broad range of azimuths are available for 1995--1997 radar observations at the Antarctic Syowa station. One event of such observations is considered to compare power and Doppler velocity of echoes at these significantly different frequencies. For the considered event, Doppler velocities of more than 600 ms-1 (as recorded at both radar frequencies) were observed. We show that even though the 50-MHz echoes exhibit strong flow angle variation of the power, the 12-MHz echoes do not. Apparent aspect angle power attenuation is found to be 10 and 2.5 dBdeg-1 at 50 and 12 MHz, respectively. Measured Doppler velocities along specific radar directions are found to be comparable in spite of the significant difference in radar frequencies, with the velocity ratio V50MHz/V12MHz being in between 1.6 and 0.9 for high velocities of more than 400 ms-1. The velocity ratio varies with slant range and azimuth of observations. Ionospheric propagation effects for radio waves and plasma physical effects for irregularities are considered in an attempt to explain several observed features, for example, the echo power and velocity ratio variations with slant range. ¿ 2001 American Geophysical Union