Abstract: A sweep frequency, continuous wave (CW) radar tank gauge (3) providing measurement of the level of tank contents or ullage (19), having greatly improved accuracy through improved methods of processing calibrate and return signals directed toward the surface of tank contents (20). Use of sweep synchronous measurement (46) of time domain calibrate/return difference signals (42) and time domain of a virtual "carrier" fundamental in the frequency domain, provide highly accurate measure of tank signal return times. The entire range of return signals is made available for processing and analysis (5), including distinguishable tank bottom reflections.