The 3585 is a 20 Hz to 40.1 MHz, microcomputer controlled spectrum analyzer. It may be utilized for spectrum analysis or network analysis (amplitude only) applications. As a spectrum analyzer, the 3585 provides a graphic display of the spectral components of the input signal. For network analysis measurements, the 3585 Tracking Generator can be used as a drive signal for the network under test. The network’s output can then be applied to the 3585 input to obtain a graphic display of the network’s amplitude versus frequency response. The 3585 is structured as a conventional triple-conversion, swept super-heterodyne spectrum analyzer. The addition of microcomputer hardware control and data manipulation greatly enhances the analytical power of the 3585 . Flexible control of the displayed trace is obtained through dedicated key subroutines that produce optimum displayed results in a minimum amount of time. Microcomputer control gives the 3585 several unique features. The most obvious feature is the keyboard entry of parameters which replaces more conventional knobs. The input attenuation and mixer levels are automatically set by the 3585 ’s Auto Range feature to maintain the specified dynamic range. Other microcomputer controlled features include: coupling of Frequency Span, Bandwidth and Sweep Time; centering of signals; moving signals to the Reference Level and storage and measurement of frequency and amplitude Offsets. Microcomputer control further allows the operator to over-ride the automatic features of the 3585 . The 3585 ’s Local Oscillator is fully synthesized using -hp-’s patented Fractional N technique. This provides frequency settability of 0.1 Hz over the 20 Hz to 40.1 MHz range. Beyond the advantage of high system resolution, the 3585 ’s Synthesized Local Oscillator allows stable, repeatable frequency measurements. The advanced design of the 3585 ’s Fractional N synthesized Local Oscillator also results in phase-continuous, linear sweeps with low spurious sidebands.