Yaesu's patented ATAS-120 Active-Tuning Antenna System provides a compact, yet efficient, automatically-adjusting antenna for mobile, portable, or apartment balcony use!Utilizing DC voltages fed from the FT-857, the ATAS-120 automatically adjusts its length longer or shorter, with the FT-857 feeding a tiny amount of power for SWR detection by its internal directional coupler.
When the best mpedance match is found, tuning automatically stops, and operation can begin. Specified for operation on the 7/14/21/28 MHz Amateur bands, the ATAS-120 contracts fully for use on the 50/144/430 MHz bands, providing a low SWR for local FM work (where vertical polarization is predominant). And if you're an apartment dweller, use the optional ATBK-100 Antenna Base Kit, which provides an outstanding counterpoise to ensure low-angle radiation on the VHF/UHF bands. See your Yaesu Dealer for details regarding suitable mounts for the ATAS-120.
