3GX with satellites.
To control gyro gain with that combination, you MUST use transmitter Channel 7 (Aux 2) to control gain. This is fixed, and cannot be changed by 3GX setup or programming.
Your DX8 chooses to use Channel 5 -- GEAR -- by default to control gyro gain when using the Gyro menu.
You MUST reprogram your DX8 to use AUX 2 channel in the Gyro menu to control gain.
When you get that set correctly, Gyro gain numbers between -100 and 0 will put the Gyro in Normal/Rate mode, and the 3GX STATUS LED will be RED.
Numbers between 0 and +100 will put the gyro in Heading Hold mode, and the 3GX STATUS LED will be GREEN.
If you don't have version 5.0 software installed, this is the time to do so. Afterwards, put the gyro in Normal/Rate mode and hover your helicopter. Adjust the tail rotor linkage until the heli will hover without wanting its nose to yaw left or right. Land, reset your travel endpoints to prevent mechanical binding.
Once back in Heading hold mode, you should be ready to fly.
Adjust gyro gain by flying the helicopter in fast forward flight. Increase the gain until the tail begins to rapidly oscillate. You will hear it, and you will see it. Then back off the gain until that behavior stops. You may need to do this for each flight mode, as gain is dependent upon head/tail rotor RPM.
* Making the World Better -- One Helicopter at a time! *