An immersion occultation of Jupiter by the moon on October 19, 1968, UT was recorded at wavelengths of 128 cm (234 MHz) and 74 cm (405 MHz) with the 140-foot radio telescope of the National Radio Astronomy Observatory at Green Bank, West Virginia. One dimensional brightness distributions are derived from the occultation curves. They show a small asymmetry in the structure of the belts. The results have been combined with observations made at shorter wavelengths to show that there is a significant increase in the angular size of the emission at the longer wavelengths and that the relativistic electron energy spectrum must have a narrow range of energies close to the planet (∼1.5 RJ). The importance of the variation of the magnetic field strength on the radiation emitted from an ensemble of electrons trapped in a dipole field is discussed.