We present a detailed study of the highest-frequency component of smooth radio emission observed during the Voyager 2 encounter with Neptune in August 1989. This emission occurs during three distinct periods on August 24 and 25, 1989, in the frequency range of 550 to 900 kHz. By assuming straight-line propagation from sources of both fundamental and second harmonic gyroemission, we perform a detailed analysis of the observed polarization of the emission. The data are most consistent with an L-O mode source in the north magnetic polar region, around 50 ¿W, 50 ¿N. A second possible source is in the north magnetic polar region, around 270 ¿W, 50 ¿N. This source must emit in the R-X mode. ¿ American Geophysical Union 1995