Congratulations repetitive TWC Today Members!
Heres where you all went wrong... 1) Victor simple asked why TWC broadcasts in Mono, not TWC HD.
HD is a completly different video carrier technology. You cant even have a subcarrier on an HD channel because HD is usually a mix minus feed, and due to the size and compression of the MPEG Video. It's possible that the HD feed is 100% communicating via VBI, and there is no subcarrier required (for old STARs) just the VBI lines on the top or side of the image.