CH Cygni in 1984-1985 : brightness fall with simultaneous increase of radio emission.

The photometric, spectroscopic and radio-flux observations during the 1984 - 1985 brightness decrease are described. The observational data are explained by use of the binary star model. An explosion of hydrogen-rich accreted matter in the white dwarf component's surface is the reason for the simultaneous decrease of the optical flux and the increase of the radio flux. The outburst became to be bipolar because it had been stopped in the equatorial plane by the thick accretion disk. The radio flux is caused by free-free emission of the outflowing gas. After the inner part of the accretion disk is emptied by the explosion, the outer parts fall down and the optical radiation decreases.