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If the Noise Sidebands test fails, check the results of the DANL TEST. If DANL is out of spec, there is a good possibility that the high average noise level is causing the noise sidebands test to indicate a false failure.
Phase Noise is a parameter that describes short term instability of LO tune frequency. Phase Noise appears as modulation sidebands near the LO. The modulation source is noise within the LO Phase Lock Loop.
A Noise Sidebands failure would indicate that noise is being injected into the LO Phase Lock Loop. The assembly most likely to be the source of the failure would be the A18 YTO assembly.
If the noise sideband is relative to a carrier frequency below 3 GHz, suspect the A9 2nd LO Assembly. The 2nd LO Assembly is turned off in highband (frequencies above 3 GHz), which means it cannot cause a problem in highband.
Failures at the 100 hZ offset are usually caused by 10 MHz Oven Controlled Crystal Oscillator (OCXO) on the A11 Reference Board.
Failures at other offsets can be caused by the A12 Synthesizer Assembly. See the PSA Service Guide for troubleshooting information on how to determine which half of the A12 Synthesizer assembly is at fault.
Another, but least likely, assembly that could cause a Phase Noise failure would be the A13 Front End Driver assembly.