Discussions

Hi community.
I have an issue with my setup and RFD900.
When the RFD900 in ON (27-30 dbi of power) the servos are tremoring and when RFD900 is OFF - all working fine.
Somehow RF noise affects to the servos or servo wires or maybe APM 2.5 and there is a tremor. I think that this is the RF noise because when I decrease the RFD900 power to 25 dbi the tremor almost gone and also when I put the RFD900 a little bit far away (~0.8m) from the APM and servo wires the tremor also almost gone, so I don’t think that this problem caused by wrong wiring or powering.
RFD900 has a separate power 5V. I tried to power it directly from the APM (5.3V) but the result was the same. Each servo gets its own power and only the signal wire connected to the APM.
My main assumption that the RF noise is affects to the servo signal extension wire and than two cases:
- the RF noise distorts the PWM which comes from the APM to the servo 
- or the RF noise affects to the APM and the APM generates a bad PWM
I also tried to connect to APM a servo with a wire about 10 sm, but the same effect.

Some videos:

https://www.youtube.com/watch?v=p0c4ieVVbZY

https://www.youtube.com/watch?v=5C0SxhVWRso

https://www.youtube.com/watch?v=P-EBhLPTP_4

Performed some extra tests.

If to place a servo which connected to a different, separate receiver - the same tremor, so it is definitely RF noise from the RFD900 affected to servo or wires from servo. If fully to cover the servo by a thin aluminium foil the tremor is gone or almost gone even at the close distance from the modem. Also I’ve been tried various settings of RFD900, nothing helps. The only way is to place modem at least 1 meter from the servos and cables, but my plane not allow to do this, or to make a super screening of the servo.