[en] Conceivably, the centres of all massive galaxies emit continous antipodal beams of relativistic particles. We shall argue that these beams consist of highly relativistic electrons and positrons. At formation, the beams plough a channel through the ambient medium; the swept-up matter repeatedly stalls the particles which thereby follow closely the ambient pressure gradient. Thereafter, when the relativistic beam particles traverse these swarms of swept-up filamentary matter, they are repeatedly forced to bypass individual filaments and radiate (in the direction of their instantaneous motion). This forward-peaked radiation pattern can explain the preferred one-sidedness of the observed radio/optical/X-ray knots in the jets. Pressure confinement focusses the beams, and temporarily freezes the channels. Interaction with the intergalactic wind can bend the beams into the shape of a warped U, on length scales above some 20 kpc. The observed morphologies of extragalactic radio sources find a common explanation. (orig.)