If you suspect there may be a break or short in your coaxial cable, check the line by testing the set-up with a new cable. If the replacement cable works, you know the original is no longer viable. The next best solution is to check the line with an ohm meter. If, however, you do not have access to additional lines of cable or an ohm meter, you can check the cable using an amp meter.
Connect the positive (usually a red clip or probe, marked with a +) amp meter into the positive (+) end of the 9V battery.
Connect the negative side (usually a black clip or probe, indicated with a -) of the amp meter to the shield (the metal ring on the end) of the coaxial cable.
Connect the metal ring or collar on the opposite end of the coaxial cable shield to the negative end of the battery, which is marked with a (-) .
Check the amp meter. If the meter displays current flow, the continuity of the cable is good.
Repeat Steps 1 through 4, clipping or touching the amp meter lead to the solid metal centre conductor (usually a copper wire in the centre of the white plastic insulation) instead of the shield. Connect the centre conductor at the other end of the coaxial cable to the (-) side of the battery as you did with the shield in Step 3. If both the shield and centre conductor have current flow, there are no breaks in the line.
Connect the positive end of the battery to the positive end of the amp meter.
Connect the negative side of the amp meter to the centre conductor of the coaxial cable.
Connect the negative side of the battery to the coaxial shield at the same end as where you made the centre conductor connection.
Check the amp meter. There should be no current flow. If the meter registers current flow, there is a short between the shield and the centre coax.