Remove the soldered connections to separate the antenna wire from the motherboard.

The antenna wire will be connected to the motherboard with 2 connections, so be sure to remove both with the soldering iron.

Follow the link below for further soldering information: How To Solder and Desolder Connections.

Soldering irons require a large amount of heat; use caution when performing this step. Excessive heat can damage parts of your device; do not leave the soldering iron on connections for extended periods of time.