Just for future reference... it's supposed to be "open".

The shields of the coax tie to the two blades of the antenna.

The center cable goes through and is open at the far end.

It's a 1/4 wave transformer... open at the far end reflects
as shorted at the end by the antenna. Put away your
E6Bs and take out your Smith Charts!

The phase reversal causes the thing to act as if it's balanced.
The length of the open end section is critical.

Bill Hale