Hi guys! This is my first instructable so sorry if it's short. I did this mod with only a foot of 24 gauge stranded wire, a soldering iron, a ruler, and some wire strippers so it's super cheap for materials. The picture is my Dronium Two, a very flashy syma X5C.
Step 1: Take It Apart
Unscrew all of the screws on the quad's body. You also have to remove the props. Then take the top off. Make sure to not lose any of the screws!
Step 2: Extend the Antenna
Locate the antenna, it's the one the screwdriver is pointing to in the picture. Strip off about a centimeter of casing off the antenna and a piece of wire. The wire must be 12.5 centimeters or longer. Twist them together then solder. Then measure 12.5 centimeters of wire starting from the circuit board then cut. I just set the new antenna in one of the arms of the quad. Double check that it is 12.5 centimeters before we put it back together because that is a full wavelength of 2.4 Ghz . The pictures might help you do this.
Step 3: Do It Again
Do the same thing for the transmitter. Twist on the wire to the existing antenna then solder. Measure 12.5 centimeters after you solder it on. Make sure it is 12.5 centimeters long then tuck it back in the remote controller. I taped it to the handle like thing but do whatever it doesn't really matter. Sorry for the wide angle pictures, the only camera I have is a GoPro. If you have a 3D printer you could print this longer antenna from thingiverse. http://www.thingiverse.com/thing:1251799 I probably will.
Step 4: Test It Out
When I first tried it i was surprised that it worked! I thought I would have messed something up for sure but nope it worked great! Got some good pictures of downtown Omaha. Thanks for reading and good luck. Post a comment if you did it. Oh, and if you have a 3D printer here is my Syma X5C collection.