Turnigy 9X8C (V2) problems

I am using a Turnigy 9X transmitter with a 9X8C V2 receiver. Because this receiver outputs PWM signals per channel, I have a PPM encoder between my flight controller (Pixhawk PX4) and my receiver. However, in QGroundControl (desktop application), I can see that the channel values are changing, but not in the correct range. This might be because of the PWM signals my receiver outputs. I see and read everywhere, that a PWM signal normally has a period of 1000-2000 microseconds. My receiver outputs a PWM signal with a period between 800-1600 microseconds.

Does anyone have any experience with this transmitter / receiver combination or could give me some directions? Thanks in advance.