From the Meraki High-Gain Omni-Directional Antenna fact sheet:
The Meraki High-Gain Omni-Directional Antenna can help extend the range of a Meraki Outdoor by refocusing the vertical signal to strengthen the horizontal signal.
This means that mounting a Meraki on a roof or second-storey with a booster antenna will actually result in lower signal strength below the unit compared with a normal antenna.
Below is the vertical polar chart of the Meraki booster antenna - so everything inside the shape is good signal strength, and you’re viewing it from side on; the optimal signal is like a big doughnut around the antenna:
As my Meraki Outdoor is mounted on my window on the second-storey of our house for optimal line-of-sight range it’s a bit tricky to actually extend the reach of the unit down to ground level … I’m currently doing some testing with the assistance of Rob who’s involved in the Free Canberra Wireless project and lives a couple of streets away.