In the C-band (4-6 GHz) receiver a 48 MHz ripple is observed in Tsys/Tcal as measured with the spectrometer and with the spectral processor. This ripple has an amplitude that varies from about 1 to 7 percent across the receiver passband. This 48 MHz ripple does not appear in the Tsys/Tsrc spectrum, which leads us to believe that the ripple is in the calibration noise source amplitude.