I often use MA-ANT-3-E6 antennes to cover ground areas if the ceiling is above 8m (in designs). Below that I'd advise you to use a downtilt omni antenna. Main advantage of the 3-E is that you get a smaller coverage cell than with an omni so if roaming is required this will give you a more predictable wireless environment. This is a MR42E with a 3-E antennes at approx 11m in a warehouse. 3-F antennes are used for getting the signal between the racks (also mounted at 11m) and standard APs at the docks (mounted at 3m).
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