IO540 you don't always have to have a socket for the external aerial available. I use an Icom A-3 tucked into the back pocket of the passenger seat. This puts the aerial the same distance from the instrument panel as the external area and seems to work well.
Kolibear I have found that the background noise in the average light aircraft is too loud to make conversation practical. Going back to he original post, in the past I have landed outside the Control Zone and phoned for clearance which was duly granted to be available within a certain timeframe.