Active amplifier GPS Antenna. High Gain MCX Connector GPS Antenna. WHY DO YOU NEED THIS ?If you have: (1) Poor reception (2) Loose reception frequently (3) Have a heat reflective windscreen (4) You want to speed up the start up time of your GPS when first locking on to satellites. Then this is the perfect product for you, this will increase the reception significantly removing any problems you may currently have with GPS reception .Ensures optimal GPS reception for your TomTom . Some specialised windscreens can block GPS signal reception inside the car. This magnetic, waterproof GPS External Antenna will overcome this limitation and ensure an optimal GPS reception. The waterproof antenna can be placed inside your car, next to your windscreen or at the back of your car. It also attaches magnetically to the outside of the car. Connect your GPS to the External Antenna and you're ready! 5 meter cable. Can boost signal by up to 400%