Linear vs Circular Polarised

Hi Everyone,
Are there any instances where a Circular Polarised antenna would be more appropriate than Linear for OpenHD?

I’m currently building a fixed wing that needs to get in behind trees, into valleys and canyons, with about 2-4km range. Outright distance isn’t my objective here.

From what I’ve read on this forum is that Linear seems to be King, yet I see DJI have gone Circular Polarised on their HD FPV goggle system which gets a claimed 4km.

An example of CP antenna that I am considering is the VAS Madmushroom V2 CP antenna which pretty much covers the entire 5Ghz range and is suggested for HD systems.

Any issues using both Linear & CP considering most RTL8812AU wifi boards support dual antennas (on both Air & Ground sides)?

I’d really appreciate any thoughts or recommendations.


Linear is not necessarily the king. It just works very well with certain digital modulation schemes. DJI did LHCP on their original air unit, but eventually went linear with their FPV drone, which flies 11+ km. And that’s because MIMO and beam forming works better with linear. Also spacial diversity works better with linear.
Combining polarization might not be a very good idea. I’m not 100% sure how multi-dongle setup is implemented in OpenHD, but something tells me both antennas are talking at the same time. If that’s the case you really don’t want to mix polarization.

one comrade wrote in a telegram,

The 5.8G helical antenna can also be used in dual polarization. Connect the left-handed polarization and right-handed polarization antennas to the ground wifi stick to obtain more stbc gain

Two helixes are quite expensive. How much do you think the signal quality will improve, is it worth it?