I see that WFLD FOX is on channel 31.
WBBM is channel 12 CBS.
Install a Winegard HD7698P antenna with the CPA-19 preamp.
Aim at about 171 degree magnetic compass.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
The antenna that is in place now and the HD7698P with CPA-19 preamp that will be installed can not be connected togather on to one coax.
A simple way to connect the 2 Separate antenna systems to the Tv is to use a remote control A/B antenna switch.
http://www.radioshack.com , # 15-1968 , or ,
http://www.mcmelectronics.com , # 32-4425 .