HGFA Operations <ops> writes:

CASA Proposal for Multicom Frequency usage below 5000ft and
Expanded CTAF's: The first element of the proposal will have little effect on our
operations. However, the second element to increase the size of CTAF's to double
their current size, is completely untenable and will severely affect and limit
our operations throughout Australia.

We have drafted a formal response to this proposal, which will be submitted to
CASA shortly and will be publish on the HGFA website.

We ask that you take the opportunity to provide your feedback, via the CASA
survey form or email, supporting our efforts to maintain your current flight
privileges.

Please go to the bottom of the CASA proposal and click on the "Online Survey"
link, then follow the directions. Alternatively, you can draft your own email
and send it to: <regulatoryconsultation>.  Please make sure that your subject
line is: "Proposal - Frequency use at low level in Class G airspace". You will
also need to provide your name and HGFA number for it to be accepted.

Please feel free to utilise all, or sections of the official HGFA response to
create your own. Thank you.

(Link
to CASA proposal)

CTAF's are essentially the controlled airspaces around untowered
(small, rural) airfields.

https://en.wikipedia.org/wiki/Common_traffic_advisory_frequency

Thanks to Scott Barrett.