The detailed analysis of Voyager observations of Saturn kilometric radiation (SKR), taking into account the polarization response of the planetary radio astronomy experiment, has allowed us to study separately the high-frequency limit of SKR emitted from the northern and southern auroral regions of the planet. Interpretation of the variations of these high-frequency limits, in the frame of a model inspired by the cyclotron maser mechanism has allowed us to demonstrate unambiguously the existence of a ''magnetic'' ''anomaly'' postulated for years, in the near-surface Saturnian field. Its location and amplitude are estimated, and it is shown that, although it accounts for the observed SKR modulation. It could not be detected by the spacecraft-borne magnetometers which passed to far from the planetary surface. This demonstrates that the current degree of comprehension of planetary radio emission makes them a unique and very pertinent tool for the fine study of planeatry magnetic field. ¿American Geophysical Union 1991