Millimetric Ground Based Observation of CMBR Anisotropy at $\delta =+28^{\lowercase{o}}$

Results from the third campaign of a ground-based multi-band observation of the millimeter emission of the sky from Tenerife (Canary Islands) are presented. The instrument consists of a 0.45 meter diameter off-axis telescope equipped with a 4-band multi-mode $^3He$ cooled photometer working at 1.1, 1.3, 2.1 and 3.1{\notetoeditor{These are effective wavelengths}} mm wavelengths. The beam is well approximated by a Gaussian with 1$% ^{o}$.35 Full Width Half Maximum (FWHM) at all wavelengths. The wide wavelength coverage of our instrument allows us to characterize and reduce both the atmospheric and galactic contamination in our data. The CMBR data is analyzed in 6 multipole bands whose centers span the range $\ell=39$ to $\ell =134$ at the two longest wavelengths (2.1 and 3.1 mm). A likelihood analysis indicates that we have detected fluctuations in all bands at the two wavelengths. We have evidence of a rise in the angular power spectrum from low $\ell $ to high $\ell $. Our measured spectrum is consistent with current popular theories of large scale structure formation, COBE, and other recent balloon-borne experiments with similar wavelength coverage.