This report shows the relationship between output frequency shifts and the absorption cell magnetic field during microwave power fluctuations on a commercial rubidium frequency clock. Changes in the clock output frequency relative to the 10 MHz reference were monitored as changes in the absorption cell magnetic field (0.01 to 1.0 Gauss) and changes in the cell\u27s interrogation microwave power were varied from the nominal specification (PO) at four discrete values (+1.3. -1.1, -2.2, -4.OdB). The maximum normalized output frequency shift of 1.4x10-10 occurred at--4dB. The maximum normalized frequency change for the +1.3 and -1.1 dB data is about 3 x 10-11, and for the -2.2 dB data is about 6 x 10-11. As a function of the change in microwave power, the maximum frequency change is about 2.6 x 10-11 -per dB of power change. There also existed several magnetic field values which resulted in minimum output frequency change. This occurred at absorption cell magnetic field values of 9 and 27 milli-Gauss, where the nominal setting is 137 milli-Gauss
