Originally Posted by
EddieHeli
... Wouldn't have felt able to get a mayday in on that frequency on that occasion...
That is the bit I don't understand. When someone blathers on for 20 seconds with their life story pretty much everyone else shuts up. If you make your Mayday 20 seconds long no one will be talking by the time you finish. You don't need to wait for a gap to push the transmit button, sure you will step on someone, but everyone else will stop and if you speak slowly and clearly you will get through.
Also, I have the impression that the centres MUX together the various feeds from antennas and can use the differential signal strength to do a better job of pulling some information out of a two at once transmission than we can in the air.