The required hardware is the L-com 2.4 GHz 14 d Bi Flat Panel Antenna with RP-SMA connector.
A good magnetic mount Omni-directional antenna such as the L-com 2.4 GHz/900 MHz 3 d Bi Omni Magnetic Mount Antenna with RP-SMA Plug Connector is a good choice.
External antennas come in a variety of shapes, based upon the usage and with a variety of connectors.
All external antennas must have RP-SMA connectors that are compatible with the Alfa.
These are not to be used in Florida, Kentucky, or Minnesota unless you are a person who holds a current amateur radio license issued by the Federal Communications Commission.