Hi Szabolcs,
Only now it occurs to me that Option 001 is only exactly like the Options 001 in so many HP instruments: High Stability Oscillator (OCXO)! Until now I thought that it (also) contained some special (PLL-) circuitry, tuning or performing whatever trick to be able to spec. the phase noise. I hadn't even looked it up in the catalog...
I'd think the lower phase noise from an OCXO source only applies at higher frequencies, not at frequencies like a few Hz, where apparently, PLL influence drowns out the OCXO's good phase noise specs. At jitter amounts in the tens of ppm's at LF, the only good the OCXO could do is less phase jitter into the PLL (control) circuitry. Is the incoming (reference) phase jitter the main/only component? IOW, is the frequency reference source the main/only cause of the huge phase noise at LF?
Raymond
