Power spectra of the residuals in T (top), E, (middle) and B (bottom) divided by the power spectrum of the input sky. Shown here are the results of the analysis of the complex-beam simulation, by the three different beams. The red, green and blue points show these different analyses using the true, elliptical and circular beams, respectively. As the true beam, including its side-lobes, spans some 15° all scales are effected by the beam; as seen in the figures in the large difference between the fractional errors of the analysis performed using the true beam and the analyses using the elliptical and circular beams. The fractional errors of the analyses using the elliptical and circular beams, are seen to diverge from the scale at which the difference between these two beams becomes important.