Keysight N9923-90001 User’s Guide93DTF (Distance to Fault) MeasurementsDTF Measurement Settings—Bandpass Mode (Default setting) The frequency range of a DTFmeasurement is set manually. Use Bandpass mode when the DUTcontains a diplexer or other filtering device which does not passsome frequencies.Typically, you will set the frequency ra nge of the measurement to the passbandof the filter. However, you may also want to test the ability of the filter to rejectunwanted frequencies. In this case, set the frequency range to include thosefrequencies which the filter may not be adequately rejecting.When the DTF frequencies are set manually, they may not be the optimumfrequencies for measuring the distance to fault. The distance may no longer bealias-free. Learn more about alias-free range on page 98.How to manually set Frequencies in Bandpass Mode— Press Freq/Dist— Then Min Start Freq and type the start frequency to use for the DTFmeasurement.— Then Max Stop Freq and type the stop frequency to use for the DTFmeasurement.— OR— Press More— Then Max Freq Span and type the frequency range to use for the DTFmeasurement.— Then Center Frequency and type the center frequency of the range to usefor the DTF measurement.These settings specify the minimum and maximum frequencies to be used forthe DTF measurement. These exact frequencies may not be used, but anarrower frequency range may be used that will still pass through thebandpass filter.To see the frequencies that are used in the DTF measurement, press MeasSetup 4 then Settings then Next Page. The calculated Start and Stopfrequencies determine the exact frequency range being used.Coupled FrequencyWhen both a DTF and non-DTF measurements are present, this setting allowsyou to have different frequency ranges for each measurement. Learn more in“Coupled Frequency” on page 84.
