  We describe and compare two types of microwave sky simulations which are good
for small angular scales. The first type uses expansions in spherical
harmonics, and the second one is based on plane waves and the Fast Fourier
Transform. The angular power spectrum is extracted from maps corresponding to
both types of simulations, and the resulting spectra are appropriately
compared. In this way, the features and usefulness of Fourier simulations are
pointed out. For $\ell \geq 100$, all the simulations lead to similar
accuracies; however, the CPU cost of Fourier simulations is $\sim 10$ times
smaller than that for spherical harmonic simulations. For $\ell \leq 100$, the
simulations based on spherical harmonics seem to be preferable.
