I'll be back with a correction. Because of a soldering mistake the antenna actually was not connected to the receiver. I put an photo to explain what I did wrong. There are an place where can solder antenna wire. But this place need to be connected with coil pin nearby. Now with right soldering i have over 20m range with single wire antenna, length aprox. 34 cm (half wave length)
Because i discover this mistake quite late i don't have time to repeat test with dipol antenna, but i will do that when will have more time, just as curiosity.
I don't have an additional antenna on my RF receivers. I put a simple single 17cm wire antenna on the transmitters. I get 200meters reliable transmission through a few trees.
Since your goal is just 15-20m, and some people here seem to disregard your project scope and are telling you to waste a lot of space, I'd take all of the advice with a grain of salt.
The fact that you only get 2meters as-is is pretty low. You showed several devices. Which one do you have? What transmitter are you using? What messages are you sending? What are your power sources? What actually is your project?
In first post a say exactly what i have and what i want to buy. In post #20 I made a correction because I explained that there was something wrong with antenna soldering. Now I have no problem with receiverl that I have.
