The modal expansion of a class of stochastic spherical scalar sources is studied. At the surface of these sources the cross-spectral density is assumed to be homogeneous, in the sense that the power spectrum is position-independent and the spectral degree of coherence depends on the angular distance between points only. It is shown that for any such source the modes are given by the spherical harmonics and the associated eigenvalues can be evaluated by solving simple integrals. Three examples of the spectral degree of coherence for this type of sources are given for which the eigenvalues can be found in closed form.