and

At frequencies close to 1 GHz the sky diffuse radiation is a superposition of radiation of Galactic origin, the 3 K relic or cosmic microwave background radiation, and the signal produced by unresolved extragalactic sources. Be-cause of their different origin and space distribution, the relative importance of the three components varies with fre-quency and depends on the direction of observation. With the aim of disentangling the components we built TRIS, a system of three radiometers, and studied the temperature of the sky at! 0:6, 0.82, and 2.5 GHz using geometrically scaled antennaswith identical beams (HPBW 18 " ; 23"). Observations included drift scans along a circle at constant declination " þ42", which provided the dependence of the sky signal on the right ascension, and absolute measure-ment of the sky temperature at selected points along the same scan circle. TRIS was installed at Campo Imperatore (latitude 42"260 north, longitude 13"330, elevation 2000 m a.s.l.) in central Italy, close to the Gran Sasso Laboratory. Subject headinggs: cosmic microwave background — diffuse radiation — instrumentation: miscellaneous — radio continuum: galaxies — radio continuum: ISM 1