The general expressions for an analysis of signal and fluctuation parameters and characteristics of an autodyne oscillator are obtained, which is under an influence of the proper reflected emission from a radar object. The oscillator model represented by a parallel connection of an oscillating system and an active element with the soft impedance characteristics, also takes into consideration the internal noises of the active element. The analysis results are presented for dependences of autodyne mentioned parameters and characteristics versus the oscillator operation mode and a value of the “softness” index of its impedance characteristics of the active element. Investigation results are necessary for engineering calculation of parameters and characteristics of the autodyne on the Gunn diode and other active elements base.