With a lot of car brands, a car antenna integrated in the heated rear windscreen is being increasingly used for
reception purposes, as a means of avoiding the mechanical problems which
may arise with rod antennas. The objective in its design is not,
however, to find an optimum geometric shape for printing on the rear
windscreen, but rather to use the existing heater-demister as an
antenna.
See for example this patent:
http://www.google.com/patents/US4736206 (
"Windshield glass for a vehicle, having heating conductive wires and antenna wires").
I did not check my Black Up! regarding this aspect. However, for example my BMW manual expressly states:
"Depending on your vehicle's equipment, the upper wires serve as an antenna and are not part of the rear window defroster." And indeed, two or three upper wires of the heated rear windscreen of my BMW do not defrost.
So check whether the upper wires of the heated rear windscreen of your Up! are
antenna wires, prior to deciding to replace the rear window. If affirmative, you risk to have
exactly the same phenomenon afterwards and you will realize that the tailgate/windscreen replacement was absolutely without reason !
Edited by: Collas