Studies of flare stars at radio waves are an important task of modern radio astronomy. They are connected with investigations of the physics of the stellar wind and stellar-planetary interrelations including habitable zones. One special interest is the search for radio emission bursts at extremely low frequencies (decameter wavelength). According to the analogy with the solar bursts the low frequency stellar bursts radio emission are arising in the outer stellar wind. Simultaneous observations at low frequencies and higher frequencies (from centimeter to meter wavelengths) are important also for the improvement of the detection reliability as well as for the phenomenology studies. We demonstrate the possibility to observe flare star bursts in the decametric radio band with the 70-meter dish radio telescope RT-70 (Evpatoria, Ukraine).