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Abstract

A portable spectrum analyzer using frequency synthesis is used in the field to perform voltage amplitude measurements of specified channel segments in a multichannel configured coaxial cable environment. The instrument is a microprocessor (28) based system, and includes an RF input (1) and keyboard (36) and function switch inputs and provides both aural and visual outputs by means of a speaker and an LCD display (27). A three stage frequency converter (7) including PLLs (11, 12 and 13) controlled by the microprocessor (28) allows for the automatic monitoring of a plurality of carrier channels or the display of both video and audio levels of a single channel. Automatic adjustment of the input signal level is provided by attenuator pads (2 and 3) controlled by the microprocessor (28). Calibration is also automatically controlled by the periodic injection of a signal of predetermined level from a noise source (4) under the control of the microprocessor (28). The microprocessor is programmed to provide several modes of operation including a sweep mode, a zoom mode, and a memory mode. In the sweep mode, the instrument continually scans all carrier channels automatically, each channel being presented sequentially and simultaneously in bar graph form on the LCD display (27). In the zoom mode, a single channel is displayed with both video and audio levels side by side. In the memory mode, the operator can view data saved from measurements previously made at a selected location in the cable system.

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First Claim