4G antenna is used if you plan to insert a SIM card into the SIM card holder and use a data plan to access the internet directly on the device. If no SIM card, then no need for the antennas.Next couple of questions:
I've got 2 4G antennas (and 2 outlets on the back of the head unit). Do I need both? Anyone know what a 4G antenna is used for?
I wouldn't put it there, ideally you'd want it under the windscreen on top of the dash, but that's ugly and a layer of plastic won't hurt the signal. So get down into the passenger footwell and if you reach up in the dash directly behind the head unit, there's a small ledge just under the top of the dash, i just stuck it there with some 3M sticky pads. signal is good.The GPS antenna, I was thinking of putting that in the headliner by the dome light (I have a spider). Does it matter which side is up? Where have some of you put it?
Yes, this connects to the reverse light power and tells the head unit to switch to reverse mode. But the red cable attached to the RCA video cable is how you do that. You then also need to connect power to the camera using cable you don't have in the picture, should plug into the red female plug and the other end is ground and reverse light power.