4. 100,000 antennas for maximum wifi power

At 10 meters away, how many receiving antennas do I need to setup to get that full 100mW power all back to me?

First, it's important to understand that receiving antennas do not add up power linearly, because they can interfere with each other due to the overlapping of their coverage areas. This is known as antenna diversity.

In an idealized, theoretical scenario where you could perfectly combine signals without any loss or interference, you would calculate the number of antennas needed based on the amount of power each antenna receives.

From the previous calculation, a single antenna 10 meters away would receive about 1μW (0.001mW) of power. The original power transmitted is 100mW.

Therefore, to capture the full 100mW with antennas each receiving 0.001mW, you would theoretically need 100mW / 0.001mW = 100,000 antennas.

But this is highly impractical and not feasible in a real-world situation due to the complexities of radio wave propagation, interference between antennas, and physical constraints. There's also the fact that antennas have a limit to how much they can capture based on their effective aperture, and adding more antennas will not necessarily increase the total amount of power captured if they start to interfere with each other.

In practice, it would be better to use techniques such as increasing the gain of the antennas, using directional antennas, reducing interference, or using multiple-input and multiple-output (MIMO) techniques to improve the signal quality and data rate, rather than trying to capture the full transmit power.