All Frsky receiver default antenna is black color from middle of 2015.
The other length is still gray color, such as 250mm, 400mm, 600mm.
FrSky receiver, and all other 2.4Ghz receiver if with ipex 1 connector for replacement
Frsky/Futaba receiver is two antenna with diversity function, only one better signal receiver antenna working at same time, please note the antenna location:
a. The two antennas must be kept as straight as possible. Otherwise it will reduce the effective range.
b. The two antennas should be placed at 90 degrees to each other
This is not a critical figure.
But the most important thing is to keep the antennas away from each other as much as possible.
c. The antennas must be kept away from conductive materials, such as metal and carbon by at least a half inch. The coaxial part of the antennas does not need to follow these guidelines, but do not bend it in a small radius.
d. Keep the antennas away from the motor, ESC, and other noise sources as much as possible.