The Laboratory of the Radio Spectroscopy ( LRS ) of the Special Astrophysical Observatory ( SAO ) has been created in 1970 as a part of the Main Astronomical Observatory ( at Pulkovo ) of the USSR Academy of Science. The first head of the LRS was N.F.Ryzhkov.

First spectral observation with the North sector of RATAN-600 took place at December 23, 1975 year. Absorption and distribution of emission intensity of 21 cm radio line were observed in the region of Orion Nebula with angular resolution of 2^' x 20^' and in the Cygnus A.

Parameters of the antenna sector in the whole region of hights were obtained with a help of a set of standart sources. On the hight of Orion Nebula such sources were 3C 218 ( F = 37.4 J ) and 3C 273 ( F = 41.2 J ). The width of a antenna beam was 2.^'2 x 20^', the effective area was 900 m².

The computer controlled radio spectrometer is operated on quasy zero method with double comparing.

The results of measuring in the 20 spectral channels, continuum channel and comparing channel were registered on the punched band in the 10-bit code.

The reduction of punched bands was fullfilled on the M-222 computer. As a result we had the antenna temperature curves in the 20 spectral, continuum and comparing channels on depend of right ascention.

On the 24-th of February, 1976 we obtained the observation of Orion A with the south sector and plane reflector of the RATAN-600.

Figure 1. Drift curves on = -5^o 25^' 16^" ( the center of Orion Nebula ).

Upper curve - continuum channel.