The periods (0.05-2.5s) generally decrease with the observing frequency as 1/f, i.e., the pulsation-frequency is proportional to the observing-frequency, presumably corresponding to the local plasma frequency. However, a detailed analysis of distributions reveals in the range 200-600 MHz at least two distinct classes of PFS periods, but the previously mentioned 1/f dependence is still maintained for the shorter-period branch (typically 0.3 s at 237 MHz down to 0.15 s at 408 MHz). The longer-period branch (typically 1 s at 237 MHz down to 0.4 s at 408 MHz) has a lower occurrence rate and shows periods inversely proportional to the frequency squared. It should be stressed that the distribution of periods derived during a single PFS-rich type IV burst is similar to the one derived for the whole data set. Moreover, we found that the distribution of periods is similar for emission-type and absorption-type PFSs. The pulsation amplitude depends primarily on the peak-flux of the smoothed-background emission (power-law with the exponent around 0.6-0.7, the exponent only weakly increasing with the observing frequency). The pulsation amplitudes are comparable, or several times smaller than the background flux at low background fluxes, and are for 1-2 orders of magnitude smaller than the background at large fluxes. This ratio, as well the amplitude itself, does not depend on the increasing pulsation period.
Finally, we present a specific morphological class of pulsations, showing a complex pulse-substructure. The substructure of individual pulses is preserved through the entire pulsation train, implying that it is not a superposition of two (or more) types of emissions, but rather a real substructure of the pulse, intrinsic to the emission mechanism.