On 28 November 2020, in uncontrolled Class ‘G’ airspace, an Airbus A320 inbound to and in contact with Ballina and an en-route light aircraft tracking abeam Ballina both listening out on a shared Common Traffic Advisory Frequency (CTAF) did not recollect hearing potentially useful CTAF calls and converged on intersecting tracks with the light aircraft TCAS only selected to Mode ‘A’. The A320 received a TCAS TA but neither aircraft visually acquired the other until the minimum separation of 600 feet with no lateral separation occurred. Changes to the air traffic advisory radio service in the area were subsequently made.