Abstract: A continuous wave FM range measuring apparatus for transmitting a signal F which is linearly modulated by a sawtooth signal over a frequency excursion .DELTA.F during a duration T and which has a central frequency f.sub.1. A phase loop is provided for stabilizing .DELTA.F and f.sub.1 with the precision of a quartz oscillator. A mixer produces a beat signal f.sub.b between the transmitted signal F and a received signal F' reflected from an object. The frequency f.sub.b and the phase .phi.b.sub.o of F.sub.b at the beginning of the sawtooth ramp are measured. The distance is calculated, preferably by means of a microprocessor (10), by first calculating an approximate value d.sub.1 of the distance d to be determined between the radar and the object as a function of .DELTA.F, f.sub.b and T. Then a more precise second value d.sub.2 of d is calculated from d.sub.1, .phi..sub.bo and the value f.sub.o of F at the beginning of the ramp. In a preferred embodiment, the level of a liquid in a container is measured.