DANL is a noise measurement which is made with the IF Detector. The IF Detector sits at the back end of multiple RF Downconverter and gain stages. Each Downconverter and gain stage adds noise to the signal. Effective DANL uses corrections (based upon the signal analyzer noise figure model) to calculate the noise that is present at the front panel connector. The frequency response corrections are essentially the conversion loss of the signal analyzer under specific conditions. The noise figure model uses frequency response corrections as one of the correction terms.
If the signal analyzer passes the DANL Test but fails the Effective DANL Test, then test the frequency response. If the Frequency Response Test passes, this suggests the frequency response corrections are accurate. For Option NFE, perform the Effective DANL Adjustment . For Option NF2, perform a manual noise floor characterization. To do this, press System > More > Advanced > Characterize Noise Floor.
If Frequency Response Test fails, this suggests that the frequency response corrections are no longer accurate. Perform the Frequency Response Adjustment followed by the Effective DANL Adjustment. If Effective DANL still fails, then refer to the Service Guide.
If the Preamplifier On DANL fails and the DUT has Option 543, 544, or 550, with a preamplifier option of P03, P08, P13, or P26, and the instrument firmware is below A.10.51, then upgrade the DUT to the latest instrument firmware and repeat the test.