The USM-8D is a low cost frequency agile modulator developed for use in adding satellite, VCR, or security video channels to an existing home distribution system. It allows the addition of channels over the Ultra band and UHF band of frequencies at an extremely low cost. The modulator has a double sideband, 7dBmV minimum output that is free from spurious distortions. The microprocessor controlled Phase Locked Loop circuitry allows selection of the output channel to be made from the front panel. The selected channel number is displayed in the channel selection window. The agile design provides maximum flexibility while allowing installers one model to cover the Ultra band and UHF channels.