  We use numerical simulations to investigate the behaviour of the dipole
moment of the spatial distribution of different kinds of mass tracers. We
select density peaks of the simulated matter distribution with mean separations
of 38 and 30 $h^{-1}$ Mpc to represent two samples of rich clusters of
galaxies. We extract, from the same simulations, samples selected to mimic the
full 3D galaxy distribution of IR galaxies, and the flux--limited IRAS and QDOT
galaxy samples. We compare the dipole moments of these ``galaxy'' and
``cluster'' samples in order to assess the effects of sampling uncertainties
and shot--noise on the relationship between the ``true'' underlying galaxy
dipole and the dipoles obtained for clusters and for the flux--limited galaxy
samples. The results of this analysis demonstrate that the dipoles of both the
IRAS and QDOT--like catalogues should trace the full 3D dipole shape fairly
accurately, with the loss however of about 15--20$\%$ of the total 3D dipole
amplitude. Furthermore, using a simple argument based on linear perturbation
theory, on the linear biasing assumption and on the amplitude of the cluster
dipole relative to that of galaxies, we can estimate their relative biasing
factors quite accurately and in agreement with results obtained by other
methods.
