Preliminary investigation of joint action of MW discharge and discharges of wide frequency range - from DC to laser - are carried out experimentally. For this purpose flexible experimental complex, including impulse powerful MW generator (500kW, 13GHz), cw SHF generator (500W, 2.45GHz), cw RF unit (350W, 40MHz), impulse NdiYAG laser (532nm, 130mJ/pulse) and impulse DC was assembled. Each unit in this complex operates both as a separate source and in combination with others. Present investigation was aimed mainly for testing of ability of different discharges, which consume low power for their maintaining, for ignition of impulse MW discharge of sub-breakdown intensity. For the first time the effect of very strong interaction of free microwaves with an external plasma channel, created by pulse air spark was revealed. Optic data reduction has been used for determination parameters of different discharge types, such as MW discharge and impulse spark. Emission spectroscopy of DC spark shows the presence of atomic lines N II and O II, thus, Stark broadening technique was applied. It gave the electron temperature in a spark channel of about 32000 K (2.8 eV) and electron concentration n_e= 1.5-10¹⁶cm ^-3. Also interaction of high-power MW with RF and MW plasmas, produced by cw generators, was realized. The possibility of laser spark initiation of microwave discharge in quiescent air under the atmospheric pressure has been investigated.