The observations were performed in January and March 1994 and in April
1995 with the Nançay radiotelescope. The halfpower beamwidth of the
instrument at 18 cm is 
in right ascension and 19' in declination. The
system noise temperature is 45 K at zero declination. The antenna
temperatures were converted to flux densities using the efficiency curve of the
radiotelescope which is 0.9 K/Jy for point sources at zero declination.
An autocorrelation spectrometer consisting of 4 banks of 256 channels with a
spectral resolution of 2.25 km 
was used to observe simultaneously
both circular polarizations of the two main OH lines at 1665 and 1667 MHz.
The observations were made in the frequency-switching mode with a velocity
coverage of 140 km 
. Sources with known radial velocity in CO line
or strong masers were observed with higher velocity resolution. The typical rms
noise level after one hour of integration time was about 0.02 to 0.03 Jy.