If I remember right, the ATAS is a HF auto tuner of sorts, usually used
for the yaesu mobile antenna...Sounds like he's trying to feed a mobile

whip with the auto tuner, at home. But just guessing...BTW, the FT-100
is
all band...HF-VHF-UHF...Kinda the yaesu equal to a icom 706....MK