We verify the relationship proposed by Kijak and Gil (1996) for the pulsar radio emission altitudes

(see also Eq.3 in Gil & Krawczyk, 1996), using the pulse-profile Effelsberg raw data at 1.41 GHz. We measured profile pulse-widths at the lowest intensity level corresponding to 0.01% of the maximum intensity (Fig. 1b), using the polarlog-scale technique (Hankins and Fowler, 1986). We calculated opening angles (Fig. 1a) and emission altitudes (Fig. 1c) assuming that: i) pulsar radiation is narrow-band with radius-to-frequency mapping operating in the emission region, ii) pulsar emission is beamed tangentially to the dipolar magnetic field lines, iii) the extreme profile wings originate near or at the last open field lines.