Abstract: A radio distance measuring equipment emits a frequency modulated carrier wave signal, having a periodic frequency deviation .DELTA.F and a mean frequency F.sub.o, toward an object, and receives a portion of the carrier wave signal reflected by the object. A beat signal produced by mixing the emitted and received signals is applied to a control loop which determines the distance. Operation of the equipment is periodically interrupted, under the control of a microprocessor, to effect calibration of the frequency deviation and the mean frequency.