IF by tap into the cable you mean disconnecting the cable service and substituting your own antenna, you could add a broadband amp to the line if signal levels are too low.
If you mean attach while cable system is still in service there are two problems.
1 - It is illegal because your antenna will radiate the cable signal. FCC really frowns on this and cable systems are required to periodically search to leaks. This would be a LEAK.
2- The cable system will already be using those channel allocations and you will get a mess.