There are newer version of this oscilloscope: DSO DS213.
I watched fiew reviews of DS203 and maximum analog bandwidth is limited to sinusoidal signals, for square shaped signals safe approximated maximum bandwidth is about half of declared 8MHz and even for slower signals readings will be significantly distorted.
My bad. DS203 has 8MHz bandwidth, DS202 has only 1MHz. So... I suppose real and usefull bandwidth will be even more smaller, something about 200-400kHz...