title_body: What makes mushroom antennae so good at receiving and transmitting omnidirectionally? I've seen many references saying that mushroom antennae (like the one shown below) are excellent at receiving and transmitting omnidirectionally. I have them on my drones' video transmitters and one paired with a patch antenna on my FPV goggles.
  
  What makes them so good at this?
upvoted_answer: The primary purpose of using circularly polarised antennas is the rejection of out of phase video reflections. They tend to have lower gain compared to linear antennas but linear need the antenna alignment to be maintained. On aircraft that flip and roll in all axis and also fly near buildings ETC circularly polarised antennas with the analogue transmission is very advantageous however with digital transmissions reflections can help.