I'm tinkering on a cheap chinaware alarm center which receives signals from its detectors on 433MHz. It is located inside a metal box which forms a faraday cage and apparently reduces the range too much. Moving the alarm center out of the box is not an option because the surroundings are very dusty, I'd like to just extend an antenna out of the box.
I found the receiver on one corner of the PCB, it's a SYN531R.
A conducting path forks off L1, passes a first solder point, goes some 4cm straight up, then 90° right and ends after another some 14cm straight on a second solder point. Apparently, the path between the two points acts as antenna.
My plan is to solder a cheap antenna directly to the PCB, however, I'm no pro, so here are some questions:
- Is this antenna a valid choice?
- Intuitively, I'd solder the external antenna onto the first solder point, then interrupt the rest of the printed antenna with a cutter. Once done, there's no way back anymore, so maybe there's a less intrusive solution: Could I solder the external antenna onto the first solder point and leave the printed antenna intact? Or maybe solder the eternal antenna onto the second solder point (at the end of the printed antenna)?
- As for GND of the external antenna: Can it be soldered onto any solder point carrying GND on the PCB or does it have to be the GND pin of the SYN531R?
Here's a photo of the PCB:
This is the schema taken from the SYN531R datasheet:
Thanks a lot for your hints!