Isn't the aussie CB band UHF?
That makes a big difference.

An HF repeater can cause interference pretty much worldwide.
UHF would only cover a few 10's of miles.
We have the same issues with 6 meter and 10 meter repeaters, though they are
legal for hams.

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KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR