First welcome to Cruiser Log >
On the assumption that you diagnosis is correct - that is to say the antenna bearing has a fault, unknown at this moment , until thoroughly checked out. Some options :--
1. If possible get some penetrating oil into the bearing's moving parts (an oil with MoS2
- Check the belt's alignment to the bearing. If the bearing is totally sealed then replace it.
2. If the bearing is A ok - then apply a belt dressing to stop slip. Something like this CLICK HERE
The main object is to isolate the faults - one by by one.
The proposition to use a drive belt that runs at a greater tension - may be ok for a time - but has the potential to cause eventual damage because it was not in the design spec.