We had a guest speaker at our 4wd club meeting last night by a uhf guru from Electric Bug here in Adelaide.
In his talk he was saying that 80ch and 40ch uhf's don't really talk to eachother that well.
Since that it will be law that you're not supposed to use 40ch after 2016, there is no time like to present to upgrade should to an 80ch so we will all be on the same frequency. Also we may use one of the higher general use channels for the trip due to the fact there may be less traffic on it eg: ch65.
Below is a list of what the different channels are used for too just for reference: