The choice between linear and circular polarization fundamentally depends on how your aircraft moves through the air. Circular polarized antennas transmit the radio wave in a spinning pattern, either clockwise (right-hand circular polarization or RHCP) or counterclockwise (left-hand circular polarization or LHCP). Linear antennas send the signal in a single plane, either vertical or horizontal.
For racing and freestyle quads, circular polarization is essentially mandatory. When you're doing flips, rolls, and flying at crazy angles, your drone's orientation relative to your receiving antenna is constantly changing. A linear antenna loses massive amounts of signal when rotated 90 degrees from its paired antenna. I've seen pilots lose video completely mid-roll with linear setups. Circular polarization maintains consistent signal regardless of your quad's rotation around the signal path. You'll typically lose only 3dB when mixing polarizations accidentally, versus the 20-30dB drop you'd see with cross-polarized linear antennas.
The standard in FPV racing is RHCP, though LHCP works identically well. The key is matching your video transmitter antenna to your receiver antenna. If you're flying with others, stick with RHCP since that's what 95% of pilots use. This matters because using opposite polarizations (RHCP transmitter with LHCP receiver or vice versa) gives you natural interference rejection from other pilots' video signals.
Linear polarization has one legitimate use case: long-range fixed-wing flying where your aircraft maintains a relatively stable orientation. Some pilots flying 30+ kilometer missions use linear antennas because they can provide slightly better range (about 1-2dB gain) when perfectly aligned. But even a 15-degree bank angle starts degrading that advantage.
In practice, I run Lumenier AXII antennas (circular) on all my racing quads and have never regretted it. The reliability through acrobatic maneuvers is worth far more than any theoretical range advantage from linear. I've crashed, tumbled, and flown inverted with zero video breakup that wouldn't have happened with the same quality linear setup. Unless you're exclusively flying wings in steady orientations, circular polarization is the only sensible choice for FPV video transmission.
