Do some basic conductivity tests on the cables - although you'll need a multi-meter for this:

1) Check there is NO conductivity between inner and outer conductors of the coax. Conductivity = short circuit = no signal

2) Check for continuity on all cables - both inner and outer (separately of course!). You should have good conductivity = zero ohms.

3) Check continuity between the TV end of the cable and the aerial end of the cable. Important: disconnect the cable from the aerial before you do this.

That should give you a clue.

JJ