When i just build in the radio, i didn't put the pjug from the GPS into the unit far enough, so the nab was indeed using the phone GPS. In the settings, i saw the unit's GPS wan 'not connected', so i took the AppRadio out, and connected the GPS antenna correctly. In settings, he now sees 10+ sats, and '3D positioning'. Unfortunatly, no speed. I do recall the GPS did read the speed, when it was using the iPhone's GPS.
The GPS antenna is mounted in the same spot where my previous antenna was, which always worked fine.