  We discuss inverse problem of detection turbulence magnetic field helical
properties using radio survey observations statistics. In this paper, we
present principal solution which connects magnetic helicity and correlation
between Faraday rotation measure and polarization degree of radio synchrotron
emission. The effect of depolarization plays the main role in this problem and
allows to detect magnetic helicity for certain frequency range of observable
radio emission. We show that the proposed method is mainly sensitive to a
large-scale magnetic field component.
