From measurements of the Jovian decametric activity that was recorded by Voyager 1 and 2 we have obtained new information on the locations of the Io-related sources A and C (i.e., Io-A and Io-C) and on the shapes of their emission beams. In two instances we were able to identify the same dynamic spectral arc event in the recorded data of the two spacecraft, providing in each case an opportunity to observe the same emission beam over a wide range of frequencies from two considerably different directions. In the analysis of such a pair of correlated Voyager 1 and Voyager 2 spectral arcs, the arc centroid time was measured at each of a series of frequencies for each spacecraft, and these time values were then replotted as a function of frequency after the source-to-spacecraft propagation times were subtracted from them. It was found that the propagation-corrected centroid times of each of the Voyager 1 arcs were coincident with those of the corresponding Voyager 2 arc in a particular frequency range, but not at other frequencies. From this information we have confirmed that the emission beams are in the form of thin, almost conical sheets, the cone opening angle decreasing with increasing frequency. We have also demonstrated conclusively that both the Io-A and Io-C sources were located near the northern foot of the magnetic flux tube that was connected to Io. By incorporating polarization information we conclude that the emission from both sources was in the X mode (both being right-hand polarized at all frequencies). However, for other Io-C arcs noted on the Voyager 1 record that were located near the one we investigated, the polarization sense reversed as the frequency decreased below 15 MHz. We suggest that below this frequency the emission mode had changed from X to O for these arcs. ¿ American Geophysical Union 1992