Description

The Drake VM2551 Video Modulator is a vestigial sideband unit with synthesized visual and audio carriers. The VM2551 is designed to accept video and audiobaseband signals from a satellite receiver, video server,VCR, camera, or similar equipment. Front panel video and audio level controls and overmodulation indicatorspermit setting the proper modulation levels. Synthesized operation provides complete frequency agility, allowing front panel selection of any standard, HRC, or IRC, CATV channel from 2 to 78 and channels 95-99 or OFF AIR TV channels 2-27. FCC required channel frequency offsets, for aeronautical channels of zero, +12.5 kHz, or +25 kHz are selected automatically and offset positive when offsets are required. The modulator accepts standard (sync negative) polarity video at a 0.7 -1.5 Vpp level. A high quality IF SAW filter eliminates adjacent channel interference. IF loop-through capability in the VM2551 supplies an IF output prior to channel conversion. This feature provides the capability to replace the standard internally generated IF output with an alternate source of composite IF, or allows insertion of IF scrambling equipment. The internally generated aural carrier may be disabled by moving an internal jumper and an external 4.5 MHz carrier can can be inserted via the rear panel 4.5 MHz input. These features, combined with a carefully designed low intermodulation output stage, provide reliable operation in a densely crowded SMATV or cable environment.