  We investigate the high-energy (HE) ($<1$GeV) emission from the pulsar PSR
B1509-58 and its relation to the radio emission in the 1.4GHz frequency band.
The role of the quasi-linear diffusion in producing the pulsed HE radiation is
investigated. We show that by means of the cyclotron instability the relatively
low frequency waves excite, which due to the diffusion process influence the
particle distribution function and switch on the synchrotron emission
mechanism. We argue that the coincidence of HE main peak and the radio pulse is
a direct consequence of the fact that the high and low frequency radiation is
produced simultaneously in a local area of the pulsar magnetosphere. In the
paper we also consider the absence of the radio counter pulse and explain this
fact.
