@luciedigitalni @colinfry666 @timrichards @Ex_spurt @skribe @danielbowen @si_fuller I vaguely remember also being able to pick up the audio from ABC TV on an FM radio in Western Victoria somewhere.
The added bonus of having TV stations in the FM band in rural areas is that even if the picture quality was too degraded, you could still at least 'listen' to TV shows.
Here's some more background info I found on channel 5a. Apparently, rural South Australia wasn't the only place it was used:
"The extra channel, likewise channels 0 and 11, were added to Australian TV dials from 1961 as it was apparent that the previous 10-channel spectrum was not going to be enough to sustain a growing television industry.
"Usage of the channel 5A frequency was restricted to country areas — mostly used by ABC, such as in Newcastle and Wollongong, but also for some low-powered translator stations for commercial broadcasters.
"There was one commercial station that was allocated 5A for its main signal — Riverland Television Pty Ltd in South Australia — hence the call-sign RTS5A.
"The company was informed by the Australian Broadcasting Control Board (ABCB) in August 1975 that it had been granted a licence to operate a commercial television service in the Riverland district, including towns Renmark, Loxton, Berri, Bermera and Waikerie. The station’s coverage was estimated to reach around 29,000 people — making it one of the smallest TV markets in Australia.
"The region was already covered by national broadcaster ABC, which had launched ABRS3 in the area in 1971, and enthusiastic viewers may have attempted long distance reception from Adelaide or from STV8 in north west Victoria. Ironically, STV8’s parent company Sunraysia Television Ltd was an unsuccessful applicant for the Riverland-based service, with the government instead opting to elect the company with 80 per cent ownership from within the Riverland district."
https://televisionau.com/2016/11/remembering-channel-5a.html