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Antenna Background Information

The antenna is a critical component in any wireless communications system.  Using a high performance antenna system will generally result in faster transfer speeds, fewer drop-outs and greater reliability.

Other factors, such as ease of installation and the desire to achieve a covert appearance, can also be important, although these often involve compromising by accepting slightly reduced performance. 

We offer a wide range of vehicle-mounted antennas to suit all requirements.  The information on this page should help to guide you towards the most appropriate antenna choice for your application, but please contact us to discuss your requirements in detail.

Antenna gain and cable loss

The gain of an antenna is a measure of how well it converts electromagnetic radiation, such as radio waves carrying a 4G signal, into electrical power.  Gain in general is usually expressed in units of Decibels (dB), with antenna gain being expressed in dBi.  The "i" denotes that the gain of the antenna in question is being compared to that of a theoretical antenna known as an isotropic antenna.  An antenna with a gain of 2 dBi will provide 2 dB more gain than an isotropic antenna.  Put simply, an antenna with a higher gain figure will perform better if all other factors are equal.

Antenna gain is not the only factor to consider though, since the signal still needs to be transferred from the antenna to the vehicle PC or router – by means of a cable.  Since no cable can transmit a signal without some level of loss, the radio waves become weaker as they travel along the cable, reducing the signal gain by a certain amount for every metre of cable.  The level of cable loss can be controlled by using high quality cable and minimising the cable length.  For this reason most of the antennas we supply are provided with ultra low loss cabling, and we can also provide crimp connectors so that the cable can be cut to the exact length required during installation. 

For all our antennas we list not only the gain of the antenna itself, but also the approximate loss in dB for every metre of cable. 

All our GPS antennas are active models, which means they include an amplifier that significantly increases the gain, making cable length and quality far less important than other factors such as the antenna's location. 

Antenna location

From the above information, one might conclude that the best solution for 4G & Wi-Fi antennas would be to reduce the cable length to zero, and connect an antenna directly to the vehicle PC or router.  However, this would ignore the fact that the antenna would then be located inside the radio wave-inhibiting metal shell of the vehicle. 

This explains why a fixed in-vehicle PC or router with a high-performance antenna solution will always out-perform a mobile phone or tablet with internal 4G antennas, or a USB dongle connected to a laptop.  Firstly, even after taking into account the cable losses incurred over a 5m cable, the external antenna solution will provide more gain than the miniature antenna inside a mobile device or USB modem.  Secondly, the external antenna is located in the optimum position - outside the metal shell of the vehicle - and is able to transmit or receive signals to or from all directions.