The 8592A spectrum analyzer, which was manufactured in the 1980’s, has a free running 1st L.O., meaning it is not phase locked to any reference. What this means is the L.O. will drift and that makes the frequency accuracy of the instrument to not be very good. The 92A did have a feature called Signal Track that you may find useful. It is used to keep the signal at the center of the screen. Essentially, the signal track performs a continuous peak search, marker to center frequency, which will obviously change the center frequency of the analyzer as the 1st L.O. drifts. The frequency accuracy specification for the 92A was at least +/-5 MHz, plus other uncertainties like 2% of span, etc.. Typical instrument performance was better than this is most cases, but Agilent only warranted the published specification.