This is from the CBS channel 2 website in Chicago:
Why can I get all other stations clearly with my converter box and not receive CBS 2?
CBS 2's current signal has difficulty penetrating through the walls of buildings. A rooftop antenna will fix this problem. CBS 2 will double its signal power on February 18, 2009 to coincide with the switch to
DTV. The power increase will take care of any converter box issues- even if you don't have a rooftop antenna. If you have additional questions, you can email us at
wbbm-tvconverterbox@cbs.com