I'm an automotive technician working at a dealership and I am working on a car with intermittent issues with wireless communication with the tire pressure sensors which are mounted inside each wheel. I went searching for the location of the particular antenna that serves the tire pressure monitoring system. There are a number of antennas on the vehicle for different things, GPS/satellite navigation, radio, tire sensors, and more. When I did find the tire system antenna I found it was located basically smack dab top center of the windshield. And, Right next to a Florida Sunpass transponder. A sticker with some kind of RF antenna/transponder device built into it, for passing through toll roads. Now I would like very much to think my technical problem has nothing to do with that transponder. But I don't know. The manufacturer's technical assistance personnel state the specific problem I have is caused by some source of EMI on the vehicle, commonly aftermarket accessories, and EMI only. Further it is clear that some types of windshields or glass tints affect RF/EMI and wireless functionality: http://www.eham.net/ehamforum/smf/index.php?topic=71368.0 This leaves me pretty confused. Does a windshield enhance the operation of an antenna? The other issues that I have had have been intermittent problems with the vehicle's only unshielded network (single wire). Low speed communication, no real protection from EMI. https://www.sunpass.com/specialWindshields That site even lists some vehicles with special windshield considerations for the transponder. Here the claim is made that the Sunpass has to be attached to the windshield: https://www.sunpass.com/sunPassInstallation Installing SunPass Mini Sticker Transponder The SunPass Mini Sticker Transponder cannot be hand-held or moved from car to car. It must be permanently mounted to the inside of the windshield or it won’t work, because the windshield acts as an antenna. Once removed, the Mini will no longer function and cannot be reattached to the windshield. indicates a fileClick here to see Mini Transponder Installation Instructions. Can someone explain the electrical technical theory about how the windshield has any relationship to radio waves? This car has run me ragged with a multitude of electrical problems of an illusory, transient, and intermittent nature. If the windshield had no bearing on antenna operation, why did the vehicle engineers place the tire monitoring system antenna there?! Thanks for any help understanding this technical issue.