Dipolar waves are launched onto the surface of a positive column afterglow. Dispersion characteristics are obtained over a more extensive range of parameters than previously examined; phase velocity, &ohgr;/kz, ranged from 0.94cto 0.27cand signal frequency is high (&lgr;0≈2&pgr;R). The waves are forward near the light line (&ohgr;/kz≈c), but become backward waves as &ohgr;/kzdecreases. Experimental results are compared with an analysis that uses the full set of Maxwell's equations (nonquasistatic) but which adopts a dielectric‐clad homogeneous plasma cylinder as a model of the discharge tube. This analysis qualitatively predicts the major dispersive features. In particular, as circumference to free space wavelength ratio, 2&pgr;R/&lgr;0, increases, the magnitude of group velocity in the backward wave region decreases; also the peak in the dispersion curve becomes less sharp and its position recedes farther from the light line. However, lack of quantitative fit between experimental results and analytical predictions indicates the need for a theoretical model which accounts for plasma inhomogeneity.