This Cage can sometimes result in poor voice quality and even dropped calls. A well-installed external car antenna usually fixes the problem. And if you're in a rural area that's on the periphery of the GSM coverage range, or even in a building that tends to block GSM signals, there are some novel antenna solutions available. The most popular though are the installed stick-on types. These external antenna housings usually consist of a base with a screw-on antenna rod.
Some rods have an enclosed coil in the middle.
Longer rods of around 50cm usually have a dB level of around 5dB, the smaller 9cm types around 3dB or less. Whatever their length, the antenna rods should be attached to a positionable, swivel-type joint on the base to allow the rod to be positioned backwards and forwards, left to right to optimize efficacy. The back window however is the most popular antenna position, although this invariably depends on the vehicle's shape. Some of the longer antennas tend to create high-pitched whistle effects in winds. 9 cm front-window mounted antennas are perfect for avoiding these situations.