86 Keysight N9923-90001 User’s GuideCAT (Cable and Antenna Test) ModeReturn Loss MeasurementsReturn Loss MeasurementsReturn loss can be thought of as the absolute value of the reflected powercompared to the incident power.When measuring an OPEN or SHORT, all incident power is reflected andapproximately 0 dB return loss is displayed.When measuring a LOAD, very little power is reflected and values of 40 dB to60 dB are displayed.The minus sign is usually ignored when conveying return loss. For example, acomponent is said to have 18 dB return loss, rather than –18 dB.How to Measure Return Loss— Connect the jumper cable or any adapter used to connect the device undertest (DUT).— Select Preset then Preset Returns the FieldFox to known settings— Select Mode then CAT/TDR (Cable and Antenna Test)— Then Return Loss (Default measurement).— Press Freq/Dist and enter Start and Stop frequency values of themeasurement.— Press Meas Setup 4 then Settings to make appropriate settings beforecalibrating.— Disconnect the jumper cable or DUT and press Cal 5 then follow thecalibration prompts.— Reconnect the jumper cable or DUT.— The return loss trace is displayed on the FieldFox screen.1-Port Cable Loss MeasurementsWhile all cables have inherent loss, weather and time will deteriorate cablesand cause even more energy to be absorbed by the cable. This makes lesspower available to be transmitted.A deteriorated cable is not usually apparent in a Distance to Faultmeasurement, where more obvious and dramatic problems are identified. ACable Loss measurement is necessary to measure the accumulated lossesthroughout the length of the cable.
