Are you sure that your "monitor" does not have an ATSC integrated digital tuner? There is a technical difference between devices advertised as digital tuners as opposed to digital converters. The Zenith DDT901 is a digital converter. It receives digital signals and converts them to analog which is the transmitted to your analog TV commonly over RF Channel 3 or RF Channel 4. No more HD. A digital tuner also receives digital signals. A tuner may be able to communicate with the monitor via component video, DVI, or HDMI. The upshot is that a digital tuner preserves your HD programming. The downside to a digital tuner is that it is more expensive than a digital converter. However, the Zenith is expensive as digital converters go. The
ChannelMaster CM7001 is the type of set top box that you want for just a few dollars more than the Zenith.