Here are reliable converter boxes ,
http://forum.tvfool.com/showthread.php?t=380 , if it's a simple plane jane converter box it will have 480i output. Here are the digital broadcast Tv resolutions , 480i , 480P , 720P , 1080i , 1080P . Also read and understand about , REAL Digital Broadcast Tv Channels , Virtual Digital Broadcast Tv Channels , Analog Broadcast Tv Channels ,
http://forum.tvfool.com/showthread.php?t=695