Variations in the Balmer decrement (BD = Hα/Hβ) as a function of the radial velocity for month-averaged spectra of 3C 390.3. Upper panel represents BD from the period of 1995–1998, and bottom panel from 2007. These two panels are chosen because they represent the characteristic behavior of BD vs. velocity. The abscissa (OX) indicates the radial velocities with respect to the narrow components. The position of the blue, central and red peaks are marked with blue, black and pink line, for Hα (solid line) and Hβ (dashed line). The rest of the panels are available electronically only.