How to get full picture on CRT television sets

[uncleputz]

We have two "Cozi TV" channels down here. One is on 5.3 and has the old format that gives a black line on the sides of a flat panel screen. The other on 51.3 is in the new format, that gives black lines at the top and bottom of a CRT set. I believe the 4.3 version will give a full screen on a CRT TV without any converter box if I use cable. Cable works just fine on my old TV's except for the black lines. I can get an RCA rf modulator at Walmart for $25. Will one of those work to give a full screen on CRT sets if I use cable? Where did I get the part about using a VCR/DVD player? I appreciate everyone's input on this.