sleeve antenne choke
you say there is not ground plane. But that is an impossibility. For current to go into the antenna, there has to be an equal and opposite direction current going back towards the source. In something like a coax line, this is more obvious--the forward traveling current can be thought of traveling on the center conductor, and there return current can be thought of traveling on the outer conductor shield. In this sorts of a feed, for a monopole, you might not want current flowing back on the outside of the ground shield, but instead want 100% of it flowing back on the inside of the coax ground shield. So, some put a transmission line sleave on the outer coax ground shield to stop the outside currents from flowing.
You seem to have a different feed mechanism, but still want to use a choke to do "something". Not sure what you want to do, but obviously a better description is needed.