314 Keysight N9010A EXA Service GuideL.O. Synthesizer/Reference TroubleshootingA16 Reference Assembly DescriptionA16 Reference Assembly DescriptionPurposeThe A16 Reference Assembly provides the fundamental reference signals fromwhich all instrument local oscillator and synchronous timing signals arederived The reference board also uses these same signals to generate CW andmodulated RF calibration signals and a 10 MHz time base signal for theinstrumentFor analyzers with serial prefixes ≥ MY/SG/US5648 the Reference assemblymust be replaced as a single assembly, although it is constructed of twoboards, the A16 Reference Main board and A16A1 Reference Daughter board.These boards are listed individually in the Show Hardware screen, allowingidentification of the individual board part numbers comprising the completeassembly.The reference signals and local oscillators can be phase locked to a timebasein one of two ways:1. The internal 10 MHz reference located on the A16 Main Board.2. An externally provided reference such as a house standard or the referencefrom another instrument or a base transceiver system. The externalreference can be any RF signal in the range of 1 MHz to 50 MHz, -5 dBm to+10 dBm.If an external reference signal is within 200 Hz of the specified externalreference frequency and Freq Ref In is set to Sense, the analyzer willautomatically switch from SENSE:INT to SENSE:EXT.The frequency accuracy of the analyzer is directly tied to the accuracy of thefrequency reference that is being used.Diagnostic LEDs monitor the status of the various PLLs on the A16 ReferenceAssembly.
