The A31 antenna is designed to help maintain tracking of GPS, GLONASS, BeiDou, Galileo, and differential correction signals in challenging environments. At times, it may be impossible to keep the antenna level away from electrical noise. A31 offers superior noise reduction with a metal base, lower profile, improved multipath mitigation, and the ability to filter out an additional 30 decibels of radio band frequencies. The A31 is designed for use with Hemisphere GNSS Crescent® and Crescent Vector™ II receivers.