N9030B PXA Signal Analyzer Service Guide 157RF Section Troubleshooting (RF/Microwave Analyzers)TroubleshootingTroubleshooting a Low Band ProblemRefer to the RF Lowband Path Block Diagram in Chapter 13and follow theinstructions in the settings box. To enable the internal 50 MHz, −25 dBmcalibrator signal press Input/Output, RF Calibrator, 50 MHz.The Low Band signal path (sometimes referred to as Band 0) is used for allsignals less than 3.6 GHz when the analyzer is used in normal operation. If thestop frequency is set to 3.6 GHz, the analyzer displays only the Low Bandsignal path. If the analyzer stop frequency is set above 3.6 GHz and the startfrequency is set below 3.6 GHz, the analyzer will sweep up to 3.6 GHz in lowband and then automatically switch to the high band path above 3.6 GHz.A11 Low Band Switch VerificationDisconnect W8 from A13A1J2. See Figure 4-3 for location of connector. Attacha right angle sma adapter to W8 and measure the output of the Low BandSwitch with a spectrum analyzer. Expected signal is 50 MHz at −35.3 dBmsince the Low Band Switch and Option LNP SW3 have a few tenths of a dBloss.If the signal level is incorrect, remove A10 Input Attenuator B output cable andmeasure the output power. Expected signal is 50 MHz at −35 dBm. See Figure4-3 for location of attenuator. If the attenuator output signal is correct but theLow Band output at W8 is incorrect, suspect the A11 Low Band Switch, theinterconnect cables, Switch 3 if Option LNP is present, or the control signals.The control signals are explained in Chapter 6, “Front End ControlTroubleshooting”, on page 199.
