can see the resultant $\sigma_{Sky}$ may be explained either by a cosmological signal existence or by the spectral index variation within $\Delta \alpha \approx 0.5$.

Unfortunately the available data give no way to estimate the variation with required precision. For more reliable conclusions it is necessary to have the sensitivity many times better than COBE instrument has.

We tried to estimate the spectral index variation crude. For this purpose we use both the COBE data and 19.2 GHz survey (Boughn et al., 1992). We has converted latter data to a COBE beam shape (Wright et al., 1994a). After that we analyzed the frequency dependence of the most intensive spherical harmonics and determined the accuracy of the estimation.

The data are shown in Table \[indx\] where one can see correspondingly: analyzed frequency ranges, spectral index $\alpha$ for desired signal/noise ratio equal to 5, spectral index variation $\Delta\alpha_5$, and the predicted spectral index variance $\Delta\alpha_N$, calculated basing on the noise analysis. In addition there are shown the spectral index $\alpha_W$ and its variation weighted-mean for all harmonics with $m\ne0$ for $l=2k$ and with $m\ne1$ for $l=2k+1$.

It may be noticed the absolute value of the spectral index $\alpha_{19-31}$ is regular lower than 