OUTPUT FREQUENCY VARIABLE MODULATOR FOR CATV

摘要

PURPOSE:To secure high C/N (carrier against noise) even in a CATV terminal by eliminating the influence of the noise even when plural modulators are used. CONSTITUTION:A synthesizer oscillator 36 is used as a local oscillator for a frequency conversion circuit 35 and a microcomputer 38 decides the oscillation frequency of the synthesizer oscillator 36 based on the set information of an output frequency setting switch 37. In this output frequency variable modulator for the CATV, a frequency band pass filter 44 is attachably and detachably provided through input/output connectors 42 and 43 between the wide-band amplifier 40 of a final stage and an output terminal 41. The frequency band pass filter 44 is set at 6MHz band in the case of the television of an NTSC system and is set at 300kHz band in the case of FM and noise components generated in other frequency bands are interrupted.