This is an antenna tuner that matches S-Line Collins
gear. It is housed in as new condition Collins 51S-1 receiver cabinet.
This 51S-1 cabinet is a late model cabinet and it has a plastic finger hole
and plastic trim ring. The antenna tuner is mounted on an internal chassis
so there is no modification to the 51S-1 cabinet except for a ground lug
on the rear of the cabinet (see pics). The antenna tuner was professionally
constructed by the late Bud Vandergriff. He did an awesome job in contructing
it. It is based on the schematics contained in the 1974 ARRL handbook page
584 and the August 1976 QST magazine page 18. See also the 1980 ARRL handbook
page 199. The antenna tuner is The Modified Ultimate Trans Match and is
an excellent design. It covers 3 through 30 Mhz and will handle one kilowatt
+ of power. This antenna tuner works great and is easy to tune up.