we lose a spherical functions orthogonality on the rest sphere part. As a result the harmonics begin to influence each to other. The problem may be solved partly using a new basis which is orthogonal over the rest part of the sphere ( Gorski, 1994) or is orthogonal only to a monopole and dipole because the excluding of these two components effects the most spectrum modification. The spectra obtained this ways may differ from a real one (Bunn et al., 1994) and may cause the essential different conclusions when interpreting the results.

A modern multi-frequency experiments seemingly allow us to separate the blackbody CMB radiation component from the frequency dependent Galaxy foreground. But variations of the radiation spectral composition prevent the procedure from being performed with a desired accuracy.

We propose the method of the spatial spectrum analysis which allows to reach the most spatial resolution without any loss in the reciprocal harmonics orthogonality. The method implies that the CMB filtering stage is conducted not before but after the radio map is expanded to spherical harmonics.

There are two filtering stages in the proposed process. The first stage is a spatial filtering one when some components related with the Galactic 