Upgrading the Linksys WRT54GS antenna
The Linksys WRT54GS comes with two factory-installed omnidirectional external antennas, which are good for indoor usage. They are both located on the router's back and can be easily detached. The free sockets/connectors can be used to attach higher gain omnidirectional antennas or directional antennas, in order to extend the acess point's communication range. Usually, only one new antenna is installed and the other socket is left empty, because harmonizing two antennas is rather difficult. The new antenna will be connected to the WRT54GS through a cable, which is called a pigtail. There are two connectors: One that connects the WRT54GS with teh pigtail, and another that connects the pigtain with the antenna.
In general: Try to keep antenna cables as short as possible and use as few connecotrs as possible as they all reduce the signal strength.
Connector WRT54GS -> Antenna Cable
Linksys uses the RP-TNC antena connector for most of its products ('RP' stands for 'Reverse Polarity').