Start by hollowing out the coupler. there is a press fit ring on one side holding it together. just hit the insulator on the opposite side using a wood dowel and hammer. it wont take much
There is a small ridge the keeps the insulator at the end of the pin. you will need to remove that from one side. The easiest way to remove it is to chuck it in a drill and file it off
Then you can cut the edge of the outer casing to make a small tab.
Then reassemble the guts but without that ridge the insulator will go all the way down I cut the edge to match that depth. a little 2 part epoxy on top will keep it together.
Now you can solder on a BiQuad of about 1.2 inches per side and find a suitable reflector. there are so many articles about sizing and tuning i wont go into that here.
I used a 5 1/4 floppy drive platter for the reflector. Other stuff like steel switch plates work too as well as regular chassis mount SO-239′s. i think the coupler makes adjusting the reflector position easier
These can be used as is or preferably used with an old satellite TV dish. just mount this in place of the original ant/lna box. N or SMA connectors would have been a better choice but i had already modified some older usb adapters to use PL-259's