On most P.I.P. televisions the main picture is from cable or satellite. The smaller picture usually comes from an antenna for "over the air" signal. I use my TV this way.
Now if you had a separate cable-box used for a second television it might work if connected by coaxial cable to antenna input. However; you would not receive HD signals this way (HDMI needed for HD). If you want a second cable station use another TV & cable box.