But the video envelope of weather echoes bears little resemblance to the transmitted pulse, and it is far from obvious that the spectra should be identical. We set out to demonstrate this equivalence, first by conducting computer simulations of an idealized weather echo (allowing us to control the properties of the simulated signal) and computing its spectrum, and then by analyzing some data collected with the CSU-CHILL radar (now available in the form of digitized IF with sub-pulse-duration sampling rates). The simulations demonstrate that analysis of a very long length of record (hundreds of times the pulse duration) is needed to begin to bring out the sinx/x character of the spectrum. Averaging of multiple spectra, which can be based on shorter records, turns out to be a more effective way to bring out the nature of this spectrum.
Processing the digitized IF data collected with CHILL during stratiform precipitation substantiated the basic conclusions of the simulations. However, reflectivity variations along the beam, coupled with the limited lengths of record available and the limited size of the data set acquired, prevented a clear demonstration of the underlying sinx/x nature of the echo spectrum.