Hello and sorry for the delay in my response. With respect to your question about the connection of the radio antenna, I confirm you that is not connected to the Udoo. The car antenna is composed of two antennas and two different connections that keep connected to the car radio. I have kept the original radio because I connectivity and steering wheel controls the entry line radio connect the audio output of the Udoo. I use the radio as an amplifier. I know that the project that appears in Hackster.io is not complete, but I'm trying to expand it. If you have any questions please do not have problem to ask. A greeting.
