  Recently published results \citep{kijak2011b} indicated the evidence for a
new aspect in radio pulsars spectra. We studied the radio spectrum of PSR
B1259-63 in an unique binary with Be star LS 2883 and showed that this pulsar
undergoes a spectrum evolution due to orbital motion. We proposed a qualitative
model which explains this evolution. We considered two mechanisms that might
influence the observed radio emission: free-free absorption and cyclotron
resonance. According to published results \citep{kijak2011a}, there were found
objects with a new type of pulsar radio spectra, called gigahertz-peaked
spectra (GPS) pulsars. Most of them were found to exist in very interesting
environments. Therefore, it is suggested that the turnover phenomenon is
associated with the environment than being related intrinsically to the radio
emission mechanism. Having noticed the apparent resemblance between the
B1259-63 spectrum and the GPS, we suggested that the same mechanisms should be
responsible for both cases. Thus, we believe that this binary system can hold
the clue to the understanding of gigahertz-peaked spectra of isolated pulsars.
Using the same database we constructed spectra for chosen observing days and
obtained different types of spectra. Comparing to current classification of
pulsar spectra, there occurs a suggestion that the appearance of various
spectra shapes, different from a simple power law which is typical for radio
pulsars, is possibly caused by environmental conditions around neutron stars.
