SatNav and Car window Technology has been changing.
Many older SatNavs require an Aerial when used in a vehicle that has the recent improvements in Car Window technology. I believe that, for some reason, there is a very thin metallic layer on recent Front windows. More modern SatNavs do not need an aerial.
I had to buy an aerial for my old TomTom, when I bought my new Peugeot Taxi Cab, nearly 4 years ago.