The IC is this one – https://www.silabs.com/documents/public/data-sheets/Si4012.pdf
It seems i have set it up correctly according to its I2C dialog with the MCU, but nothing gets received by my SDR.
P.S. @downvoters: why the hate ?
Got an answer for the hate, and more hate, excellent!
Surely enough I've spent some hours on the internet trying to figure whether these things can work without any antenna or not. Obviously with no luck. And no, the pdf linked here does not clearly make it obvious to everyone that the damn antenna can not be skipped. Actually there are a some separate pdf files describing how to make the trace antenna for this chip. I guess everybody knows, sure. Here is another link with me asking in their forums yesterday – https://community.silabs.com/t5/Proprietary/Si4012-with-chip-antenna/m-p/195937/highlight/true#M2987
Anyway, short and to the point post, maybe from a phone while in the subway ? Nah, hating is more fun.
Best Answer
No. You really can't cheat physics.
Note that some devices can even be damaged when not attaching a TX antenna, since power has nowhere to go (this is likely not the case here).
Your unconnected TXP and TXM pins will act as very very bad antennas, and might thus actually might cause problems with the rest of your system.
Really, it's not absolutely clear to me how you came to the conclusion that a radio transmitter without an antenna might be a good idea!