Spectra Precision Survey Pro v4.5 Ranger Reference Manual - Manual (Page 209)

Survey Menu – GPS Module
R-201
Note: The Post Processing screen is used to start logging with post
processing receiver types only. If you wish to record post processing
data simultaneous with RTK, then you should set the recording
interval on the Job | Settings | Post Process screen and then start
the base and rover using the Start GPS Survey wizard.
When you tap the Post Processing menu while connected to either the
RTK base or rover, you have only two options. If the RTK receiver is
already recording data, you are prompted if you wish to close the open
logging file. If the RTK receiver is not logging data, you are prompted
if you wish to clear the RTK setup and proceed using this receiver for
post processing data collection only.