From what little I know about this series of oscillators, I would guess that the equation is not intended for the 83590A unit.? It is intended for an oscillator plug-in family member that has the extended range down to 10 MHz.? The "3.8 GHz" value used in equation only makes sense for the other oscillator family members that go down to 10 MHz.? These oscillators can switch in an additional mixing stage to operate below 2 GHz.? This additional stage uses a fixed 3.8 GHz cavity oscillator.? The 83590A doesn't have the 3.8 GHz oscillator, nor can its "Fo" go below 2.0 GHZ.
Someone at HP probably did an erroneous "cut-and-paste" of the equation, from another document within that oscillator plug-in family.? Just a guess, though!
