I am making a weather station and I'm using a pair of cheap ASK modulation 433MHz RF modules to transfer data from an outdoor sensor to an indoor unit. I am using 1/4 wavelength antennas and my breadboard prototype worked well with a range of about 30 meters.
When I constructed the circuit on stripboard and mounted everything in a box the range reduced to 2 meters max. I had to mount the RF module several cm away from the main PCB, which is the only difference between this and the prototype.
Could the additional power wiring between RF receiver and main board be picking up the same signal as the antenna, and reducing the range? My understanding is that if the signal is present on both the antenna and ground line, the receiver will struggle to pick it up as there is essentially no potential difference between antenna and ground plane. Has anyone else had this issue?
There are so many variables it’s hard to address them all. What kind of case, what does your PCB look like, where was it, how were they positioned in relation to one another and to the receiver. Pictures and schematics can help answer some of those questions.
Thanks for your quick response! I've actually just moved the RF board onto the main circuit board and that's greatly improved the range. I think it must have been an issue with the ground wire.
Every quarter wave antenna needs a "counterpoise", a reference conductor such as a large ground plane. If there isn't any, the ground circuit becomes part of the antenna. Often the geometry and layout of that side of the circuit is random and variable. It will upset any tuning that you make to the antenna. That is the beauty of a dipole, it doesn't need any ground reference to radiate, and both elements can be optimally tuned for the best standing wave ratio.
If you do have a ground plane, the signal ground should be connected to that plane, at the point where the antenna is fed. Coaxial cable should be used between that and the transmitter.