This is a great write up by IBCrazy's VAS website. If you want more information check out his website as it contains a wealth of great information!
Circular polarization is used by NASA and many HAMs to communicate with satellites that orbit the Earth as the orientation of the satellite is consistently changing. This is very similar to an FPV aircraft in flight. Circular polarization has two distinct advantages: it rejects multipath interference (which is the most common reason for video issues), and does not lose polarization when a plane banks to turn. If you are having trouble with video scrambling or random drop outs, this is likely due to multipath interference. MULTIPATHING IS NOT FUZZ IN THE VIDEO! MUTIPATHING IS SCRAMBLING OR SUDDEN DROP OUTS!
When to use circular polarization:
- When where your base station is near (within 100 feet) of large structures such as houses or buildings
- When standing on a porch or deck of a house or apartment or other building
- When stunt flying
- When flying behind trees and objects
- When doing low altitude flying
- When flying very high altitude (with a directional antenna)
Linear polarization is very common and is the easiest to implement. It is capable of longer range than circular polarization, but is more susceptible to multipathing. The range advantage is seldom realized due to multipath interference. The antennas tend to be more compact and easier to build (as well as cheaper to buy).
When to use linear polarization:
- When flying out in the open with no structures nearby
- When flying planes that do not bank sharply
- When going for long distance runs
- When standing on top of a hill or mountain
- Where antenna compactness is needed