Original date: 2022-08-26

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I received the RF test PCB and soldered it. TL;DR It's not so good.

I tried different placements and a few known pi matching networks (different values of inductors, caps, etc) for the new SMD 433MHz antenna. It's definitely better than the last reversion: the received RSSI is ~10dBm better in average, but no matter how I try, it's still ~15dBm worse than a common dipole antenna. But fortunately, its performance almost didn't change after I did the assembly simulation by putting it into a real shell, with the LCD screen and the BL-5C battery installed.

The good news is, the 2.4GHz antenna is a great success. At least it outperformed the 2.4GHz antenna inside my smartphone. There's a thick wall built by cement + reinforcing steel between my room and the server room (which contains the WiFi AP, 20dBm TX power), and it has -45dBm RSSI. Bravo!

I still feel disappointed. Or I shouldn't be too strict for such a "hobbyist project"?

Another comforting news is, the manufacturer of the SMD 433MHz antenna offers free impedance matching service. But they said I need to give them the final reversion of the fully assembled device (i.e. not a bare PCB) because everything on/near the PCB affects the impedance. So this has to wait...