A cloverleaf antenna is considered omnidirectional and a helical is directional. An omni-directional antenna sends and receives signals in all directions, so it’s a great choice for video transmitters. A helical antenna produces a cone-shaped signal in front of it and has a small pocket behind it to receive a signal. It will provide better coverage
at longer distances but only if your airframe stays within the cone of the antenna. When you fly outside of this cone, reception will get a lot worse. Helical antennae are best for
long-range, usually fixed-wing FPV flying. Omni-directional antennae are best for FPV racing and close-proximity multirotor flying. Where a person flies and what they are flying with (fixed wing vs. multirotor, for instance) will determine which antenna is the best choice. – Tim Nilson, founder and owner of Lumenier and GetFPV
These are examples of cloverleaf antennae. Most of them are enclosed in a plastic covering.
A helical antenna is directional and used for long-range flying.
