The more antenna coverage brings the stronger signal? The wireless router with more antennas is better?
First of all, Wi-Fi is applied indoors, and 802.11 series protocol we often use is also established for such conditions. Due to a variety of obstacles between the transmitter and the receiver, there is probably no direct signal during transmission and receiving. We call this approach multi-path transmission which is also known as multi-path effect. Multi-path, as its name suggests, is to increase the transmission path.
Then the problem is, since it is multi-path, the transmission distance varies. Some may be reflected from the table, and some may come through the wall. The signals that carry the same information but have different phases eventually gather together to the receiving end. Modern communication adopts the store-and-forward packet switching, also known as packet switching, and the transmission code is symbol. For obstacles produce different transmission delays, there is ISI (Inter Symbol Interference). To avoid ISI, the bandwidth of the communication must be less than the reciprocal of the tolerable delay.
In short, the emission range of the wireless router is decided by the IEEE802.11 protocol rather than number of the antenna.