German Hopf 4491 Small GPS Antenna is the integration of a high performance GPS antenna and an advanced low noise amplifier in a very small size (very compact / fully waterproof housing). When connected to a GPS receiver, it boosts the antenna power with a voltage of 5V, provides excellent signal amplification, and an out-of-band filter. The small antenna is suitable for all kinds of German Hopf time servers. It has the ability to remove environmental noise very well.