TRF370417: LO spectral purity required.

Dear Sirs:  Related to an older thread (3 yrs ago) I am driving the LO port of the TRF 370417 from a synthesizer chip through a buffer amp.  The input to the LO port is not a square wave as my frequencies on the LO port go from 600 MHz to 5500 MHz. with the higher frequencies having reduced amplitude of the harmonics. Neither is my LO drive a pure CW sine wave.  Is there any advice you can offer on how "clean" i.e. harmonic content of the LO, should be?  One of your competitors specifies -30 dBC on the third harmonic.  IF there is harmonic content, which parameters are degraded?  I suspect the sideband suppression.  Your guidance is greatly appreciated.  Thanks, Charles (Skip) Robidadrt.