433MHz λ/4 Ground Plane Antenna

thingiverse

I use an ESP8266 based 433MHz transmitter to control a bunch of RF outlets. The transmitter unit is located in the cellar. I had trouble with some RF outlets far away from the transmitter not switching reliable. Far away means about 20m and several walls and ceilings in between or outdoors. I used a simple DVB-T antenna before and wanted to give a dedicated λ/4 ground plane antenna tuned to exactly 433,92 MHz a try. And yes, it made the difference. All switches, even farer away than before, are working now. This design is a simple base an top rod guide for soldering 1,5mm brass or coper tubes to a shielded coaxial cable. For short distances a common 75 Ω tv antenna cable can be used. For longer distances I recommend to use a shielded 50 Ω cable. For an effektive design the 45° angle ot the ground rods is more important than the length. The rod material can be brass or copper. Stainless steel will work too, but it is harder to solder. You need one 168mm rod for the tip of the antenna soldered to the center wire of the coaxial cable and four 170mm rods to be soldered to the shield of the cable. These four rods are building the gound plate. Depending on your transmitter and antenna cable you may try to shorten the tip down to 163mm to get better results. But for me 168 mm was just fine. The image shows the first aproach and this did work from scatch. If you have the space left I can recommend this antenna design. Otherwise a simple dipole antenna will give better results already. Have fun and good luck building this antenna.