Elimination of range-aliased echoes in the VHF radars

Very high frequency radars designed to measure tropospheric wind profiles usually detect scattering to a maximum height of about 20 km. If the antenna elevation angle is 45 degrees or more above the horizon, the maximum range of interest is less than 30 km. A VHF pulsed Doppler radar wind Profiler can, therefore, be operated at high pulse repetition rates. The maximum bandwidth allowed is about 0.5 MHz so a radar with uncoded pulses can operate with a duty cycle of 1 to 10%, depending on the desired height resolution. It is possible to operate a tropospheric wind profiler that utilizes all the average power available from the transmitter without the complexity of coded pulses. However, the VHF radar can detect echoes from the mesosphere on occasion and, with high pulse repetition rates, these echoes occur at the same apparent range as the tropospheric echoes. These mesospheric echoes may be stronger than the tropospheric signals. The range-aliased mesospheric echoes can be greatly attenuated or effectively eliminated.