The equation f(x, x1, x2, x3)=f(y, y1, y2, y3) is considered that characterizes the relation between the measured reflection coefficient x, the calibrating reflection coefficients x1, x2, x3 and the corresponding values y, y1, y2, y3 read off the reflectometer. Sum of the absolute values of the sensitivities of x with respect to x1, x2 and x3 is minimized in three ways. Minimum of the sum of the absolute values of the sensitivities equals to 1. One of our methods is applied for the minimization of calibration sensitivities in microwave reflectometers. In the experiment the sensitivity reduction by a factor of 2.5 is achieved.