The eigenspectrum plotted as a function of the number of jackknife samples N_JK (light to dark blue envelopes) in comparison to the sample covariance (dashed black line). In the bottom subplot we show the ratio with respect to the sample covariance. The solid lines represents the mean and the envelopes the spread (i.e. 95% confidence intervals) from ten realisations. Increasing N_JK improves the off-diagonal structure of the jackknife covariance although we see a bias towards higher eigenvalues for the smaller eigenmodes. For N_JK = 74 and 148 the covariance is singular, shown by the eigenspectrum dropping to zero for eigenmodes > N_JK.