  High-quality integrated radio profiles of some pulsars contain bifurcated,
highly symmetric emission components (BECs). They are observed when our line of
sight traverses through a split-fan shaped emission beam. It is shown that for
oblique cuts through such a beam, the features appear asymmetric at nearly all
frequencies, except from a single `frequency of symmetry' nu_sym, at which both
peaks in the BEC have the same height. Around nu_sym the ratio of flux in the
two peaks of a BEC evolves in a way resembling the multifrequency behaviour of
J1012+5307. Because of the inherent asymmetry resulting from the oblique
traverse of sightline, each minimum in double notches can be modelled
independently. Such a composed model reproduces the double notches of B1929+10
if the fitted function is the microscopic beam of curvature radiation in the
orthogonal polarisation mode. These results confirm our view that some of the
double components in radio pulsar profiles directly reveal the microscopic
nature of the emitted radiation beam as the microbeam of curvature radiation
polarised orthogonally to the trajectory of electrons.
