Anritsu FAQs
When I'm using my MS2711D sometimes the noise floor changes value by 25 dB. Why is that?
The MS2711D, S332D and the MT8212B have a feature called "dynamic attenuation" that monitors the overall signal levels into the instrument and, if there are no strong signals it removes all input attenuation and turns on the preamplifier. When strong signals occur it immediately turns off the preamplifier and, if necessary adds input attenuation to avoid mixer saturation. The preamplifier has a gain of approximately 25 dB, which is why the noise floor changes by 25 dB when it is inserted or removed from the signal path.
