Parametric effects in not directed antennas, installed on the helicopter fuselage

The paper shows that the system "A Standard Omnidirectional Antenna - Metal Body of the Helicopter" becomes non-parametric system at rotation of main rotor. Under this condition the effective height of the antenna is the parametric factor. Distortions of the spectrum of radio signals on the input of the standard antenna are consequence of periodic changes of the effective antenna height. In the paper, the method of analysis of signal spectrum after parametrical distortions is developed, namely: quantitative estimation of attenuation of spectral components of useful signal and detection of combination frequencies of unwanted components-satellites. Spectral distortions of some types of modulated and manipulated signals on the output of parametrical antenna system are also considered.