RF TRANSMITTER / RECEIVER MODULES

RC-16 problems

This 433 MHz transmitter/receiver pair is a very cheap way to get packet radio data from Arduino sensors. However, the transmitter unit in the photo has a problem. There should be a three-turn wire coil soldered between the second and third pins up from the bottom left. (The hole in the lower left is for a 17.3 cm (quarter wave) wire antenna. I recently bought some of these modules from another source that had the same problem -- possibly the same offshore source.

I soldered in a three-turn coil from 26 gauge phone wire and it works fine.
Also, on the receiver module, the hole in the upper right hand corner of the module is for the 17.3 cm receiver antenna. This hole appears to be soldered over -- not an insurmountable problem, but a bit of a pain. In some of the modules I bought from other sources, the right hand end of the three-turn wire coil was soldered into this corner pin, rather than the connected adjacent pin just to the left of the corner pin. Again, not an insurmountable problem, but one that makes it much harder to properly solder the wire antenna.
These modules are widely available online for as little as $2/pair. Unless you need lots of them, $3 is an OK price, but you will have to add your own coil to the transmitter.