Cloverleaf antenna is a circular polarized antenna for FPV which is way better than the cheap dipole antenna that comes with video transmitters and receivers. Antenna is one of the most important parts of FPV system. In this tutorial I will show you how to DIY one.
Omni circular polarized antenna like Cloverleaf is one of the best FPV video transmitter antennas available to hobbyists. I explained the benefits of a circular polarized antenna over a linear one if you are not sure what are the differences.
What is a Cloverleaf Antenna
The Cloverleaf is a closed loop antenna which the signal and ground wires are connected. The cloverleaf antenna has 3 loops at 120 degree apart, and they are titled at 45 degree to horizontal plane.
Good and bad things about Cloverleaf Antenna
Circular polarized antennas are great for FPV video streams because they’re good at rejecting phase shifted signals (distorted signal) such as multipath interference. The cloverleaf antenna has an excellent radiation pattern and very low gain.
It is not the ideal receiver antenna however, because the reverse polarization rejection pattern is very erratic. You need to choose other types of antennas for the receiver such as the skew planar wheel (4 lobes).
Let’s get started!
Parts you will need
- 0.8mm copper clad welding wire, it’s stiff and easy to solder (some people used 0.6mm also worked fine)
- RG316 coax cable (or RG405)
- Soldering tool
Measuring and Cutting the antenna wires
The size of the antenna (the length of the wires) does not follow the rule of “bigger, better”. The length of antenna wires affects what signal frequency you can receive. The length you need for your desired frequency can be calculated using mathematical equations. Generally the length of wires would be smaller for higher frequency signals.
To make it easier for our readers, you can use this tool to calculate the required length of the wires:
(Formula: Length in millimeter = 307022 / Frequency in MHz)
Use this tool to calculate where to bend the wires.
(Formula: Length in mm = 76755 / Frequency in MHz)
As an example, for the most common 5.8 GHz FPV system (5800 Mhz), the length of the wires should be 52.93mm, and it should be bend at 13.2mm. This is what the shape and measurements should look like.
Measure and cut 3 pieces of wires at the calculated length, cut them just a little bit longer (marked as optional above, so you have the extra length to solder to the main wire. Trim both ends so they are flat.
I bend the small piece of wire into square U shapes, and I personally don’t really leave the “optional” part in the wire.
The 3D design diagram with angles
Cut your coax cable open, so the ground and signal wires are separated, exposed and ready to be soldered.
You don’t have to follow the picture below, you could cut your fingers :)
I put the bent copper wires on some blu-tac, and arrange them according to the 3D diagram above. For example for the VTX antenna, I put them about 120 degree apart, and for the VRX antenna, that should be approximately 90 degree.
And tilt the wires to the right 45 degree. This will make the antenna “right handed” polarized, since this is a more common configuration.
Other Polarized Antenna Design
Skew Planar Wheel Antenna (4 lopes)
Virevent Antenna (4 lopes)
Windmill Antenna (5 lopes)
The key to making a successful FPV antenna is to be precise with measurement. The more accurate you can make the antenna the better it will perform.