By open stub, you mean there is no loop at the bottom of the "J"?

bob k5qwg

No, Open Stub means the 1/4 wave element and the 3/4 wave element are
not connected.

In the typical (closed stub) J-Pole I have seen the center of the coax
connected to ether side of the antenna, seems to work equally poor
ether way.

In the case of the Open Stub J-Pole I have found that a wider bandwidth
can be obtained connecting the center to the 3/4 wave element. (about
12 MHz.)
Connecting to the 1/4 wave element, bandwidth is only about 6 MHz.
The 2 meter band is only 4 MHz. so it really don't matter too much.
Try that with the typical copper pipe J-Pole.
73 Al Lowe N0IMW