Experimental results on spatiotemporal pattern formation on a ring electrode during the oscillatory electrodissolution of cobalt in 1.0 M phosphoric acid are reported; the ring is the area between two non-concentric circles and its width thus varies continuously with angle. The experiments were controlled potentiostatically with the tip of the capillary of the reference electrode placed in the center of the ring 1 mm above the surface. Under these conditions rotating waves, with and without modulation, occur. The influence of positive global coupling (in the form of an external resistor of variable size in series with the working electrode) on the pattern formation is investigated. A small added global coupling smoothes variations in speed and size of a rotating active area which are caused by the deformation of the ring and surface heterogeneities. A larger global coupling leads to non-traveling patterns including complete synchronization of the ring and also synchronization within subsections or smaller areas of the ring; these subsections themselves oscillate in a phase-locked or quasiperiodic fashion.