The AV4021 RF Spectrum Analyzer is high performance and economic, and can measure precise signal noise ratio, distortion, spurious. Its GPIB interface can realize the construction of intellectual measure system and hard-copy the measurement results. The built-in IBASIC is able to perform a second processing and judgment of the data with zero bandwidth sweep and time-gated spectrum measurement. The analyzer is used in the design, production and maintenance of communication equipments.