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If you use your cellphone in your motor-vehicle, an external cellphone antenna is a must !!

That’s because cars insulate cellphones from the external GSM signal, an unwanted artifact known as the "Faraday Cage." 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.

External antennas are available at around US$23, but are invariably professionally fitted as part of the complete installation of a cellphone car kit.

Your installer is likely to provide you either with a semi-permanent stick-on antennae design that simply sticks onto the front or back car windows using adhesive tape, magically transferring the GSM signal through the glass and then via a cable to and from the external antenna socket on your GSM cellphone or it’s special car kit.

Some installers also provide permanent boot (trunk) and car roof mount designs, but these tend to be more expensive as they invariably necessitate some car-body drilling and additional wiring. There are however many do-it-yourself clip-on designs available that don’t really require any detailed technical knowledge and can be installed in minutes. 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. Antenna efficacy is usually measured in decibels (dB) - the higher the rated dB specification, usually the better it’s performance. 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 base positioning of the antenna on the car is also important: some installers prefer the front or back window, while others drill on the car boot or roof. The back window however is the most popular antenna position, although this invariably depends on the vehicle’s shape.

Your external antenna should also feature a position lock "memory" to ensure that the antenna rod stays in the position you set it - especially when used in high-wind areas. Some of the longer antennas tend to create high-pitched whistle effects in winds. Make sure that you can also unscrew the rod: this feature is especially useful if you want to prevent the antenna being mangled by a car-wash behemoth. Smaller, low profile 9 cm front-window mounted antennas are perfect for avoiding these situations.

There are also a number of easily fitted removable/portable car antenna solutions. One design simply clips on to the top of a wind-up side window, allowing you to switch cars and still have external antenna support. Once you’ve placed the clip onto the top of the window, you then simply plug (hard wire) the attached antenna cable into the phone’s antenna socket. You can use it with the window open or closed as the cable signal is relayed to the antenna’s external rod via the window clip-on.

There is however another side window clip-on design available that does not use any hard wiring. Instead it uses a special cordless pick-up rod inside the car - also connected to it’s external rod via the window clip-on - to "passively" relay the GSM signal to and from the cellphone. With both these clip-on designs, the back right passenger window is recommended.

There is yet another flat "patch" passive antenna type that simply sticks down flat onto any window. This solution, although not the most effective, is useful in offices where GSM signals may be blocked by an abundance of concrete and steel in the wall.

If you’re in a fixed rural location on the coverage fringe, there are special 10dB corner reflector antennas that can be attached to poles or buildings.

No field assembly or tuning is required and they easily attached to your cellphone using ordinary cable connections.

If necessary, you might also want to consider special booster devices that increase the power of you cellphone from the average 2W to up to a powerful 8W.