Most vehicles today have a remote keyless entry system installed, which allows the driver to access the vehicle without a key. Older vehicles can be upgraded by buying an after market product to have the same capabilities. After market devices tend to have more range because they do not fall under the same FCC rules concerning power output. In any case, there are ways to improve the effectiveness of the antenna in the vehicle.
It does not matter if you vehicle has an after market system of it came from the plant; in each case the receiver will have an antenna attached to it. Some times the antenna is on the printed circuit board (PCB) in which case the following does not apply. If the antenna is a visible wire that comes out of the receiver, you can try the following. Locating the receiver and antenna inside the vehicle may be tricky. If you have it may be possible to create a longer antenna, which would greatly increase the antenna height. Increasing the antenna height would improve performance and increase the range from your vehicle that the FOB will work. It may be tricky but there are cases where this is possible. Your aftermarket device may be able to accommodate a longer antenna as well.
The length of the antenna does matter if you are able to fabricate a new one. In North America, the keyless entry system operates just above 300mHz and 315 megahertz. This tells you that antenna length is just less than one meter, 95cm to be exact, would be the ideal antenna length (one full wavelength) for that frequency. If the antenna in your vehicle is 24cm or 48cm long, that equates to a quarter and half wavelength respectively. A full wavelength or 95cm would be ideal.
In most cases, this may not be possible however there are still some tricks to remember. Many variables will change the performance of the keyless entry system. Unless you have an aftermarket FOB that has much higher power output in which case you may never find that you have poor performance, try the following.
The farther away the FOB is from the ground the better. The ground will reflect the signal preventing it from reaching your vehicle. Holding the FOB over your head will yield much better results. If you remember from above roughly one meter is a perfect antenna for the FOBs at this frequency, keeping that in mind your body will also act like an antenna. A person just over six feet tall is almost two wavelengths which is even a better antenna. That tells us that a tall man will have better performance than a young child who is much shorter will. Also parking away from vehicles and other obstacles will improve your range. The more objects that are between you and your vehicle the closer you will need to be for the FOB to work.
The final trick that creates great performance is holding the FOB directly under your chin. This method works well even though it is less scientific why it does. In some cases, this works better than holding the FOB above your head. Trial and error is really the only way to make sure. The last resort is to check the battery in the FOB. The batteries are designed to last for many years but keeping a fresh one in there will keep your range performance high.
Michael Russell
Your Independent guide to Antennas
Source: www.ezinearticles.com
