I just discovered that I don't have any 433MHz antennas. So I must make some.

Luckily, I had a few broken RC model receivers with long range antennas. I can modify those to run at 434MHz.

A quick calculation shows that for 434MHz we need an antenna length of 164mm (at quarter wavelength). I would have liked to have enough length to create a half-wave antenna, but that should do it for now.

It has a UFL connector already on it.