When an ionosonde sweeps through a given frequency range, the transmitted pulses may be regarded as the frequency components of a synthesized pulse. If measurements are made of the phase and amplitude of the ionospheric echoes observed over this frequency range they may be regarded as the frequency spectrum of the echo of the synthesized pulse. The range of the echo of the synthesized pulse is therefore given by the Fourier transform of the phase and amplitude measurements. Using a frequency range of 128 kHz gives a range quantization of 586 m so that echoes separated by about 1 km in range can be resolved. This paper discusses the principles of the method and presents examples of results obtained using the method.