433MHz λ/4 Ground Plane Antenna

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I control RF outlets with an ESP8266 based 433MHz transmitter located in my cellar. Some far away outlets had trouble switching reliably, especially those 20m from the transmitter and several walls or ceilings in between. I tried a DVB-T antenna before but now I'm using a dedicated λ/4 ground plane antenna tuned to exactly 433,92 MHz. It's made all the difference - all switches are working now, even those farther away than before. This design is a simple base and top rod guide for soldering 1.5mm brass or copper tubes to a shielded coaxial cable. For short distances, you can use a common 75 Ω tv antenna cable. However, for longer distances, I recommend using a shielded 50 Ω cable. For an effective design, the 45° angle of the ground rods is more important than their length. You can use brass or copper rod material, but stainless steel may also work although it's harder to solder. You'll need one 168mm rod for the tip of the antenna and four 170mm rods for the shield of the coaxial cable. These four rods form the ground plate. Depending on your transmitter and antenna cable, you might shorten the tip down to 163mm for better results. I used 168mm and it worked fine for me. The image shows my first attempt at this design, which was successful right off the bat. If you have space left over, I recommend trying out this antenna design. Alternatively, a simple dipole antenna might give you better results already. Have fun building this antenna!