B737-800 Ramp service agent reported ground damage after a collision between a power stow bag loader and an aircraft antenna. The aircraft was removed from service for repair.

Narrative

On Day; I was assigned a turn flight of Aircraft X. I marshaled the plane in and completed my post arrival walk around as procedure states. On the inbound there were about 100 bags; give or take. My team which consisted of myself; Crew Chief; Person A; and Person B downloaded the flight. Because we only had three agents on the team I ran the bags alone so the rest of my team could start the upload. By the time I returned after running the bags to claim 5 the upload had been mostly complete. Person B says to me 'I got the rest of the bags; you can start your walk around'. I proceeded to start my pre departure walk around when I noticed that the front bin was still open and belt loader was still pulled up. I asked my Crew Chief; who was stationed at the back bin loading the plane; if it was ok to close the netting and pull the belt loader back from the front which they replied yes. As I walked towards the front bin I noticed our departure time was in 2 min so I rushed over to the bin; closed the netting; closed the bin door; and immediately entered the belt loader seat to back up from the plane. I lowered the belt and put the vehicle in reverse; and the belt loader jerked; once in reverse I noticed the chocks were still on the belt loader. I relieved the pressure from the tires on top of the chocks by shifting the belt loader gears; with my foot on the brakes; and leaned over out of the seat to grab the chocks. Once I threw the chocks onto the belt loader I looked back to back up and the belt loader went forward. I was unsure how far and immediately hit the brakes as it happened. I then backed the loader up from the plane; parked it and performed my walk around. At the end of my walk around when entering the push back tug; I noticed that the antenna was bent but was unsure if that was out of place. I proceeded to talk to the Captain about push back when I saw a Crew Chief at the bag buddy near our gate and asked for his opinion on the antenna. They told me it was damaged and that we needed to call maintenance. Agent spoke with the Captain and Maintenance proceeded to check out the damage. I never truly knew what caused the damage because from what I saw at the time everything looked fine. It was not until entering the push back that I saw the damage. The belt loader unexpectedly went forward and that is due to the rushing; because of the brake pressure and placement of the equipment. I do not remember exactly the steps it took or why the loader went forward but I know certain belt loaders at ZZZ have a tendency to jerk when put in gears and is such a tight fit for a longer legged person. Getting used to those jerks and also not knowing how far it will go can throw you off in the moment. Once I realized that the antenna was off I notified the first Crew Chief I saw; and he alerted the Captain; and Maintenance. Maintenance assessed the damage and put the plane out of service. My team was asked by the manager on duty who performed the arrival and departure walk arounds to which I responded me. Then my team had another plane to work on the ground at the gate next to ours so we parked that plane and worked it. A look at the belt loaders in use because of the tight space and the effectiveness of the brakes. There are a lot of instances where that particular belt loader needs to be wiggled in a certain way just to get the belt started.