Simultaneous bearing observations were made using a cathode-ray direction-finder of the U-Adcock type and a multi-aerial wide-aperture instrument (PV2) employing cyclical differential measurement of phase. The transmitters observed operated in the frequency band 8–12 Mc/s and were located at distances ranging from 750–1500 km. In the analysis of the data, where particular attention was paid to the rapidly varying component of the bearing changes, it was found that for the majority of the transmitters studied the spread of bearings was significantly greater with the Adcock than with the other direction-finder. The reasons for this difference are discussed and it is inferred that a large part of the superior performance of the PV2 was due to its relatively large aerial spacing. Although the Adcock instrument gave the better performance in the presence of interfering signals, a higher proportion of observations were lost with it owing to deep fades.