# Quarter-wave length antenna shape

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 omni-directional.

I was told that a good antenna for small 433MHz modules is a one quarter wave length 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 such an antenna? What are the pros and cons of each of them?

• 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. Commented Dec 12, 2016 at 7:47
• do some work in 4nec2 Commented Dec 12, 2016 at 8:46
• 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? Commented Dec 12, 2016 at 9:47
• sorry, that was a typo, I edited. With 180º I mean one half of a sphere. Commented Dec 12, 2016 at 14:24
• 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. Commented Dec 12, 2016 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:

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

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:

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

• @Andyaka Much better, thanks. Your google-fu is better than mine :) Commented Dec 12, 2016 at 13:45