The Complete Handbook of TV Converter Boxes

Chapter 1: Understanding TV Converter Boxes

A TV converter box is a signal translation device. It takes a digital broadcast signal, either over-the-air (OTA) or from a cable system, and converts it into an analog format that an older television can display. The core need for this device stems from a regulatory and technical shift that occurred in the United States in June 2009, when full-power television stations ceased broadcasting in the analog NTSC format and switched to the digital ATSC standard. That single event rendered every television manufactured before roughly 2007 incapable of receiving broadcast channels without an external intermediary. The converter box is that intermediary.

To understand the device, you have to understand the signal it is translating. An ATSC broadcast is a digital stream of compressed video and audio data, modulated using either 8VSB or 16VSB (Vestigial Sideband) modulation. The data rate varies by station and by the complexity of the content, but it is generally between 19.39 Mbps for a single high-definition (HD) channel and up to 38.78 Mbps for a station broadcasting multiple sub-channels. This digital stream must be demodulated, meaning the tuner in the converter box has to lock onto the RF carrier frequency, extract the digital bits, and then decode the MPEG-2 or H.264 video compression to produce a raw video frame. After decoding, the converter box re-encodes or transcodes that digital video and audio into an analog format your TV understands, typically NTSC composite video on an RCA jack or an S-Video