Question about beat frequency of Spectr-RF

I use pss+pnoise to do VCO simulation. I set the beat frequency at the oscillating frequency from tran simulation. When I change the beat frequency to the frequency from PSS, the phase noise change worse. So which should be the right beat frequency and right phase noise?
Thanks!

Did you checked the oscillator button in the PSS form?
Mazz

Yes, I enabled the oscillator button. Does the phase noise relates to the beat frequency?