up to now I found some information for 0-10V DC out, perhaps its a similar way how to get 0-5V DC and then feed it to XTR110
"saw a previous diagram on here using a BC183 to get a 10V output which was smoothed with a RC. This circuit had the Arduino PWM port connected to the Base of the BC183 with a 4k7 resistor in in series. The emitter was connected to Gnd and the Collector connected to a 12v+ supply with a 1k Resister in series. A 680 resistor and 1 uf capacitor in series was used to smooth the output from the collector....any "small signal NPN" transistor should do with a gain of around the 100 to 300 mark. The 2N2222 has a high current rating and so a small gain but the BC547 should work fine."
found another way to get 0-5V output (example for a motor controller) here:
"you may not need an op-amp to buffer the analog voltage after low pass filtering.To create a low pass filter wire a resistor from the Arduino PWM output pin to the positive side of a electrolytic capacitor. Wire the the negative lead of the capacitor to ground. Run a wire from the junction of the resistor/cap to your analog input terminal of your motor controller. Also run a ground wire from the Arduino gnd pin to a ground terminal on your controller. Set your motor controller to accept a 0-5vdc analog command signal. As to the values to use for the resistor and cap, it would help if you had a scope to see how much ripple remains after the filter. I've had pretty good luck using a 5k ohm resistor and a 10mfd cap.
You can kind of measure the effectiveness of the low pass filter with just a DVM meter. First verify you get 0 vdc with the PWM command at 0 counts and 5vdc with the PWM command at 255 counts. While still at 255 counts, switch the meter to read AC volts and the resulting AC voltage reading is a reflection of the amount of ripple voltage."
Do You think a low pass filter like that would be a solution to feed the signal in a xtr110 or would the remaining ripple disturb the xtr110?
hoping to get about 20mA out with 255 pwm counts and adjust 0mA with 0 counts...