Buy from Amazon : http://www.amazon.com/gp/product/B007XB3D30?tag=wayofcats-20

Shure UA874US Active Directional UHF Antenna with Gain Switch (470-698 MHz)

Compatible with all Shure wireless receivers and antenna distribution systems that provide 12V DC bias
Four-position gain selector switch
Low-noise signal amplifier compensates for transmission loss in coaxial cable
Integrated threaded adapter mounts easily to microphones stands
Legendary Shure build quality and reliability