yeah, antenna is short. If you can extend it to be higher than it closes the frame with a diagonal but even then it is a bit lifeless.
But I can't really think of anything that would really help.
- Another antenna/tech/pipe on the other side (also going higher than the figure) may help, but not sure about it.
- or maybe a wall, with a bit of door frame visible to give a 3rd vertical line to the composition while framing the whole as smaller than itself.
- maybe a flagpole (without flag/some small one/flag coiled up), but that seems cheesy
the other arm's position can also change it a lot.