[Boatanchors] CU-1772/SRA-56

[Ispoulin at aol.com]

Good Afternoon; I recently acquired a surplus CU-1772/SRA-56 HF  Antenna 
Coupler ,a unit of AN/SRA-56 antenna coupler group. It is a large  manually-tuned  
NAVY rack-mounted unit with a type of   slot-shaped opening in the rear case 
which is insulated and the rectangular  opening passes between the turns of  
an inductor  inside the  tuner..  If anyone can provide some info on what plugs 
into this slot,maybe  a link  or probe  to connect to the antenna 
feedline,possibly.?? Would  appreciate any info,thankyou,Al,W1TUK