I built a simple RF communication system with a 433MHz transmitter and a receiver. The transmitter needs to transmit in a 180º range (I mean in one half of a sphere, I don't know how to say that in English), the receiver must be omnidiectional.

I was told that a good antenna for small 433MHz modules is a one quarter wave lenght wire, and also that the shape is important, but I didn't found on google what are the best shapes.

What are the possible shapes for auch an antenna? What are the pros and cons of each of them?

  • \$\begingroup\$ This is kind of like asking "what is the shape of a radio receiver". The question is too broad: there are chip, flex, PCB and all manner of wall-mount antennas. Just check any antenna manufacturer site. \$\endgroup\$ – Lundin Dec 12 '16 at 7:47
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    \$\begingroup\$ do some work in 4nec2 \$\endgroup\$ – My Other Head Dec 12 '16 at 8:46
  • \$\begingroup\$ This doesn't make sense: "The receiver needs to transmit in a 180º range". Receivers receive, transmitters transmit. Also what part of three dimensional space is defined by an angle of 180? \$\endgroup\$ – Andy aka Dec 12 '16 at 9:47
  • \$\begingroup\$ sorry, that was a typo, I edited. With 180º I mean one half of a sphere. \$\endgroup\$ – noearchimede Dec 12 '16 at 14:24
  • \$\begingroup\$ You won't find a simple antenna solution that can fully transmit in one half of a sphere. You'll struggle to find a complex antenna solution that does it also. Look at the patterns in @Majenko answer to see what I mean. \$\endgroup\$ – Andy aka Dec 12 '16 at 14:31

What you are describing is a Monopole Antenna. This should be perpendicular to your ground plane - that is pointing straight up into the air.

The radiation pattern for a monopole antenna is like this:

                                     enter image description here

That is seen from the side, so it actually looks a bit like a deformed doughnut:

             enter image description here

As you can see, the best signal strength is actually away from the antenna, not close to it. If you want better "close" coverage you can go for 3/4 wavelength which adds an extra bubble on top. Other lengths give even more bizarre shapes:

       enter image description here

In all cases the "shape" is a vertical rod.

  • \$\begingroup\$ @Andyaka Much better, thanks. Your google-fu is better than mine :) \$\endgroup\$ – Majenko Dec 12 '16 at 13:45

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