The class 3b double ribbon flare of 1980 July 23

We observed the Class 3B double ribbon flare of 1980 July 23. From our measurements and analysis we found 1) its motion can be divided clearly into 3 stages, lateral outward expansion of the two ribbons, their bodily separation with expansion and their contraction. 2) The sudden increases in the flare areas coincide in time with the peaks in the 10cm radio bursts. 3) The flare was located in a small sunspot group in an old active region. It was $\text{not}$ preceded by the disappearance of dark filaments.