Simultaneous two frequency observations of radio pulsars.

Simultaneous two-frequency single pulse observations for PSR 1133+16, PSR 1929+10 and PSR 2021+51 were carried out at frequencies 927 and 6000 MHz. Data analysis shows a systematic time shift of the mean profiles between the two frequencies when the known dispersion measures were considered. For PSR 2021+51 this shift may be explained by the frequency dependence of the main profile. The cross-correlation level between single pulse intensity fluctuations at the two frequencies was shown to be two times lower than the value obtained before at frequencies 102.5 and 1700 MHz.