Why does my local station only broadcasts primetime shows in HD and others shows in SD?

Lets says for example, channel-4 (NBC) can broadcast Heroes or Conan in HD, and Jeopardy, which although says 'Jeopardy HD' on the lower left, is shown only in 4:3 SD on the same digital channel. Why is that so? Also I notice that when the local station wants to show a weather alert map on the upper right, the picture changes from HD to regular definition [even when watching a primetime program]. Can somebody give me an explanation as to why this happens? Thank you.

PrimeRisk2009-07-07T12:55:02Z

Favorite Answer

In many cases the show you are watching wasn't produced and recorded in High Definition so they station can't give you more than they have. They may even be broadcasting it in a higher resolution, but the quality will be no better.

classicsat2009-07-07T23:03:37Z

It is because that station isn't fully HD.

The network programs like Heroes or Conan the O'Barbarian are switched into the HD transmission directly from the HD network feed..

Local programs, syndicated programs (such as Jeopardy), and emergency alerts come from the station storage, control, and overlay system, which is only SD, and the HD transmission switched to that as needed.

Anonymous2009-07-07T22:18:10Z

Because HD program is need a ot of legworks, require a HD camcorder, software also require more data to broadcast in the airwave.
However cable television like Food Network HD, almost all of their program are shot in HD.