What would the best way to combine 4 antennas into one distro, in order to provide coverage for an extremely wide area.
I have been quite successful in using multiple RX and TX antennas in one venue. To keep the Diversity you need to cover each area with the 2 channels of antennas and the antennas need to be at lease 6-30' apart - say on each side of the stage.
Multiple RX antennas in one zone do not cause dropouts, it only increases the signal so there is no need to be particularly careful in overlapping the coverage. For transmit systems minimum overlap is desirable but also has little bad effect.
The entire trick is managing the levels from your antennas. Long Coax introduces loss and in many locations you can use an amplified +10dB antenna to make up. In Hi RF level areas, though, amplified antennas cannot be used at all because they overload. Areas such as 34th street near Macy's In NYC which is less than a mile from the Empire State Building TV antennas.
Splitters and combiners need to be best quality with minimum loss. My favorites come from Mini circuits. A 1X 2 splitter at 600 mHz has about 3.5 dB loss.
Another terrific new tool is RF over fiber. It is not for the novice to use and requires a lot of careful RF level wide band measurements covering all the concurrent carriers which will be carried on the fiber. The advantage is no loss!
Here are a layout for multiple antenna system transmit and RX system which was not for Mics nor was diversity. Same could be applied to a diversity system but double.