In a magnetic resonance scanner, a main magnet (20, 22) generates a static magnetic field at least in an examination region. A magnetic field gradient system (30, 54) selectively superimposes magnetic field gradients on the static magnetic field at least in the examination region. A magnetic resonance excitation system (36, 36') includes at least one radio frequency coil (30, 301, 302, 303) arranged to inject radio frequency B1 fields into the examination region and at least two radio frequency amplifiers (38, 40, 40') coupled with different input ports of the at least one radio frequency coil. A controller (66, 70) controls the magnetic resonance excitation system to produce a time varying spatial B1 field distribution in a subject (16) in the examination region that time integrates to define a spatial tip angle distribution in the subject having reduced spatial non uniformity.