  Variations of radiocarbon concentration have been studied in annual rings for
the last 350 years (1600-1950)on the basis of our experimental research using
methods of spectral analysis. From this interval of time special attention is
paid to the so-called period of the Maunder minimum (1645-1715) of solar
activity. In the experimental series of corresponding period two types of
periodicity are revealed: 20 year and 8 year.
