where to solder antenna on 433 MHz remote control
It appears the antenna is on top of the board as shown. It is the land on the outter left hand curved edge. It is also mirrored and connected with vias to the bottom. It is connected by a capacitor and has two holes drilled in it and further down in the middle, has 3 holes. The photo darkens at the bottom so it is hard to see if it ends in space or connects to something. On the top of the board, cut the land with maybe an exacto knife just before the two holes by the capacitor and solder an equivalent length wire (or 2X, 3X etc) by the capacitor. That's my best guess from what I see. If it doesn't do the job you can scrape the surface clean on the land and resolder it bridging the gap.