The 800S is specifically designed to fit the SDS100, so it fits correctly. But most other SMA antennas will not.
The BNC adapter that comes with the radio is not supported by the collar around the SMA connector, and if you drop the radio on the antenna, you can snap the SMA connector fairly easily. I have a SDS100 in my work queue right now with that exact issue. I make and sell a SMA-BNC adapter that press-fits into the collar so that side stresses are mostly transferred to the radio case instead of the connector, and it makes breaking the connector a lot less likely. There may be other sources if you look around a bit. I'm not aware of anyone who has broken their SMA connector while using a BNC antenna and my adapter.