The factory head unit has a signal wire for the antenna so that it automatically rises when switched to radio, but stays down when set to CD, etc. Aftermarket head units have the same signal wire although some units raise the antenna when ever the unit is powered on, not just while set to radio. The Jensen above has a control wire, but not sure whether it only raises the antenna on radio.
The actual antenna cable is not part of the wiring harness. One could position the antenna where they want it, unplug the harness, and it will stay in that position without affecting signal reception.
I have an old Kenwood head unit and the antenna control wire stopped working. It would only rise a few inches. I wired the trucks antenna control wire to the head unit power wire and now it fully raises whenever I turn on the vehicle and the up/down switch works. It's a hack, but I'm looking for a new head unit, so it will only be temporary.
This past week, I thought my hack failed as the antenna was back to only rising a few inches. Before ordering the parts for the a Tundra mod below, I decided to take apart the antenna motor and see what was going on. The plastic track was just getting bound up at the gear. I pulled the track out of the side and a 12-volt jump pack attached to some alligator clip leads to run the antenna motor and eject all the track. I screwed it back together, reversed the alligator clips and sucked all the track back in. Works fine now, so the Tundra stationary antenna will have to wait.
Also, have some of the black inner fender clips on hand any time you fiddle with the antenna. I always break a couple.
Tundra antenna write-up:
Tundra Fixed Antenna Install w/ Part Numbers
Replacement mast for $15:
Toyota Land Cruiser 100-Series Power Antenna Aerial AM FM Radio Replacement Mast
Or OEM part is 86337-60150 ~$50.