Check for leakage or short between the center conductor and the shield in the RADIO CABLE.
Connect the MULTI METER as shown below:
A good cable will give a reading of infinity.
A defective cable will give a reading of some continuity.
Check for an open braid or shield in the RADIO CABLE,
A good braid or shield gives a reading of 1 or 2 ohms.
An open or defective braid gives a high resistance reading (or even infinity).