Oscillations in scan impedance over a finite array have been shown previously; here they are modeled by a Gibbs-type standing wave. The wave period derived from the transform of a single pulse with phase shift is .5λ/(1-sin &thgr;0), which closely fits simulated array data. Gibbsian models containing sine integrals provide fair to excellent matches to computer-simulated dipole arrays, with and without screen, and for E and H plane scans. The E plane scan results are new, as are those for the H plane scan with screen. ¿ American Geophysical Union 1996