HC12 communication problems

Hello everyone,

I'm actually trying to make a ringbell for my fence so people can press a button and a radio signal is send to the control center (another arduino inside my house) where a bell rang.

The problem is about the HC12 modules I use for the radio communication. Indeed, It's pretty impossible to get a single caracter successfully sent and received.

I've tried many many things, I've bought special 433MHz antennas that I've plugged on the 2 HC12 cards, I've made independant 5V sources to supply those 2 radios cards to give them sufficient power but It still impossible to make a single radio message travel trought a wall.

I don't really understand why It doesn't work because there is a very small distance and only one wall.

Do you know what else I can try? Do you also know a radio card that can do what I want to?

If I take the example of my home alarm that has 5V modules, they manage to communicate throught 5 walls without problem...

Thanks for your answers

Edit: I precise that I also configured the 2 HC12 on maximum power for long transmissions