Someone asked what the point was of having an ATZ at somewhere where there was no ATC, just air to ground. This is obviously to "protect" the aircraft in the circuit, so they can go round the circuit without having to worry about tranist traffic. Without an ATZ anyone could fly through the middle of the circuit at 500ft. Also in an ATZ all turns must be in the same direction as the circuit which makes things a lot safer.
Although I am not sure how this will "protect" other aircraft. As PIC in this situation it would be up to me how I join, what runway I use etc.....The radio operator can say "7 right hand" and I could look at the windsock and say "nah, think I'll do 25 right hand thanks". Also at a Radio field, in theory a pilot could just call up and say "XYZ radio, GABCD coming through your ATZ at 1000, good day" and there is not a lot the radio operator could do about it.
It is a complete waste of time having an ATZ around a radio or FISO field in my opinion.