  Using centimeter wave and decimeter wave solar radio spectral observations of
the flares of November 18, 2003 and September 12, 2004, we have discussed two
type II like bursts at the meter waves. The radio bursts show that the ordinary
frequency drift from high to low frequencies slows down and stops, and a
frequency drift from low to high frequencies appears. An analysis of all data
on the corresponding flares provides evidence of formation of quasi standing
fast mode shocks (termination shocks, TS). TS are able to generate energetic
electrons, responsible for the appearance of new sources of hard X ray
radiation and generation of fast radio bursts (spikes), fibers and zebra
structures. The sources of the radio emission bands with the unusual frequency
drift are situated above the top of the post flare loops (lower TS) or are
connected with the erupting prominence or coronal mass ejection (CME, upper
TS). Estimations of the critical Mach numbers for the ordinary plasma
parameters in the solar flares give the values 1.3 easily realized in the flare
events. The conditions necessary for generation of unusual radio bursts are
likely to occur in the helmet shaped magnetic structures in the solar corona.
