A three-dimensional ray tracing code which incorporates the O-4 magnetic field model (Acuna and Ness, 1976) and a realistic plasma model has been used to model high-curvature decametric arcs observed by the Voyager planetary radio astronomy instrument. Two examples of intense, isolated, vertex late, high-curvature arcs were singled out for study. The souce point wave normal angle was incremented at each of a full range of frequencies until the model rays identically matched the observed arcs of the planetary radio astronomy data. Several different Doppler shifts were assumed at the source point. By this procedure an accurate relationship between the wave normal angle &PSgr; and the frequency was obtained, with the variation being 70¿1.1) at the source point produce &PSgr;max>70¿, in agreement with the ray tracing results for the two arcs considered, only for v∥>0.7 and v∥/c>0.32 (where v∥ is the electron velocity parallel to B). Actual values of v∥/v are unknown, but independent observations indicate that v∥/c≈0.1. Since the low-curvature arcs are believed to result from larger wave normal angles, our results indicate an upper limit to the Doppler shift of Jovian decametric emissions of f/fg<1.1.