A high-performance, 100 Hz to 1.5 GHz spectrum analyzer for bench and ATE use. The exceptional frequency stability permits measurements with a 10 Hz bandwidth. This narrow resolution bandwidth yields noise levels as low as -135 dBm. Excellent frequency stability,sensitivity, and frequency reference accuracy allows very accurate measurement of small signals in the presence of large ones. Multiple traces can be displayed to measure residual FM or drift, or to conduct real-time surveillance over a wide frequency range. Analyzer control settings can be saved in non-volatile memory. Complex measurement routines can be created on an external controller, stored in the analyzer's user RAM, and executed using a single custom softkey. HP-IB.