You could solder on an female SMA connector and try to solder bridge the end of the center pin to the output capacitor. You would need to buy a 433 MHz antenna instead of using the wire antenna. You might also consider trying to solder a thinner gauge wire to the output capacitor and then securing it with epoxy to the PCB. In either case you will need a temperature controller soldering iron and will need to be careful not to use to much heat or the capacitor will come off the board. There are likely other solutions but those are the first two that come to mind.
Edit: You might also drill a small hole where the pad used to be and pass the wire through the hole and carefully solder to the capacitor. Then epoxy the wire for added strength.
<p>This is an optional SMA connector for use with Altus Metrum products that ship by default with a wire whip antenna. If you bought a board with a wire whip UHF antenna and later decide you'd rather have an SMA connector to attach a remote antenna, this