Draytek ANT-1205 network antenna Omni-directional antenna RP-SMA 5 dBi

Omnidirectional. 2.4Ghz & 5Ghz bands. Supplied two in a pack.
High-Gain Dual-Band Aerials
Set of 2 Antennas
Available in white or black
Can improve range and coverage of wireless signal
Suitable for all DrayTek routers & access Points

Wireless LAN Aerials For DrayTek Products
Vigor routers equipped with Wireless LAN facilities are supplied with the standard 2 or 3dBi gain aerials. A higher gain aerial provides a signal gain which can in many circumstances improve your wireless coverage/range as well as your connection speed at longer ranges, particularly where your required coverage area is currently borderline and needs a 'little extra help'.

Uni(single)directional aerials are intended for application where you want the signal in one direction only, either for increased range or for security reasons. By concentrating an aerial in one direction, both transmission strength and receive sensitivity are improved as well as benefits in avoiding interference or traffic from adjacent networks in other directions.

Wireless antenna gain is a complex area and we'd recommend seeking out a specialist site for further details but put simply, aerials are designed in such a way that they can increase the signal strength and receive sensitivity by concentrating into a narrower focus/beam.