A simple to construct, high-resolution, retarding field analyzer (RFA) comprising a cone-in-the-can electrode configuration was developed to eliminate the problems associated with the planar RFA, specifically potential sagging around the discrete wires of the grid and the cutoff energy dependence on arrival angle. This study extends the analysis of this spectrometer by discussing its performance as a function of its internal dimensions, specifically the length to width (L/W) ratio of the analyzer body. Experimental data for several designs are also included and indicate a resolution of the order of 1% is achievable. The simple geometry of the analyzer lends itself to miniaturization. However, the elimination of the grid from the device is an essential task if full miniaturization of the analyzer is to be realized. Such a gridless high-resolution RFA has been developed and the first results from this device show a resolution comparable to that of the grid-based design. Performance analysis of the gridless analyzer as a function of its dimensions is also reported. (C) 2003 American Vacuum Society.