This is on an OrangeRX from hobby king.
Step one: Find some wire of the same dimensions as the original antenna. In this case, its awg 24 (a lot of balance leads are this size. I always have some lying around that have been cut from old batteries.
Step two: Cut the new piece of wire to length. The wave length of 2.4ghz is 125mm. The antenna i'm replacing is 1/4 wave length, so I need to cut the wire to 31.25mm.
Step three: Trim of enough insulation to solder to your board. Remove old antenna, and solder new one in its place. Try to use as little solder as possible.
I noticed there is a second antenna pad on this board. Not sure if adding another one will work. I know the newer ORX has two antennas.
All ready for action again.
Make sure to do a range check after replacement, to be sure the signal is working correctly.