System temperature on blank sky at C-band at four different frequencies: 4000, 4040, 4080, and 4120 MHz (Scans 11, 13, 15, 17). (Postscript Version) Four 40 MHz sections of the spectral processor are concatenated. The spectral processor was used in 2x1024 mode with a bandwidth of 40 MHz. The long vertical lines are the edge of the pass-band. The scans 11, 13, 15, and 17 correspond to the OFF position in a series of OFFON measurements towards 3C286. The entire plot spans 160 MHz.