Is the Allan deviation in 53220A calculated in terms of fractional frequency, or absolute frequency? It shows no units so I suspect is fractional frequency, but I have seen pictures of the 53230A on google with Hz units. Then, I suspect the 53220A uses fractional frequency for the Allan deviation, while the 53230A uses absolute frequency for the Allan deviation. Can someone confirm if this is true?
The Allan deviation provided by the 53220A (firmware version 2.05) is calculated with absolute (instead of fractional) frequency variations. Note the real units for this Allan deviation are Hz, but the instruments shows it as unit-less.