Partial Cable. When I connect this TV to a coax cable line (not through a converter box) it only

Question

When I connect this TV to a coax cable line (not through a converter box) it only gets a signal through the first 16 channels or so, but it should be getting many more. An older Zenith on the same line gets everything.Our older Sharp tv/vcr tv worked fine before we moved now only gets up to channel 28. It's not hooked up to the cable box now, but other bedroom tvs work fine. Don't have org. remote and can get the menu to come up to try channel search but won't let you choose an option. Any suggestions?