The ATAS-120A is a screwdriver antenna by Yaesu specifically for the FT-8X7D series and FT-100 radios. This antenna is controlled from the radio itself, and requires only the RF coax line to the antenna. Configuring the radio for this antenna is done simply through a menu setting. Controlling the antenna is done with the Tune selection in the display menu. It covers the HF, 50 MHz, 144 MHZ, and the 430 MHz bands. It does not cover 80 or 160 MHz, but that is OK with me because I'm not on those bands anyway.
The only trick with using this antenna is that you must have a good ground. Depending on the vehicle, you might need more than 1 good ground. I have mine mounted on the back of my Honda Element, and I have a ground strap going from the rear door to the body. That is all I needed for this antenna on my car.
This antenna has gotten a lot of bad press about it's efficiency. Some people even say that a dummy load puts out better. I believe that is because they don't have it installed correctly. There are definitely better mobile antennas out there, but for the money, you just can't beat the ATAS-120A. Not including the 40 MHz net I check into every morning, I have over 400 HF contacts with this antenna in 62 different countries. I am even able to break through pileups for QSOs, and am regularly told that it's hard to believe I'm mobile with my signal and audio. I am very happy with this antenna.