@HUW
The stock dipole antenna's are really good and provide a nice range.
To answer your question, i really don't know anymore. We say " i am not going to stick my hands into a fire for it ".
I did so many changes i lost track.
What i first made was a collinear antenna and replaced the stock ones.
They did not preform better but i had cut off the stock ones from the coax. Due to lack off u-fl cables.
I got approx 5000ft with a collinear on the RC and bird. It could have been 7000ft. Really don't know anymore.
Anyway as i wanted @ least 2km or 6561.68ft of flawless range ( FPV and RC ) i wasn't happy with the setup because it had hiccups on its way in and out.
So i finally gave way and departed from my omni directional idea.
Up to the helicals.
As i had seen a test video with helicals and that the longer ones ( more turns ) provide as you mention also sideway control nearby i decided to make a 11 turn for the RC and a 10 turn or the wifi ( real helicals. axial mode
article here).
Especially the wifi ones that i have seen and are sold are operated in normal mode and thus are actually onmi directional antenna's.
For 2.4Ghz the round disk must be @ least 12.4cm or 4.8479 inch.
Calculate helical article here.
As i wanted to keep polarization the same ( bird and RC/Wifi ) i made the skew planar antenna's.
And this setup made a real big difference.
As the RC was the better link ( i guess ) it was time to do the wifi.
I have the RC on FCC mode now and made 2 days ago a 10 turn helical for the wifi that i range tested this afternoon.
I had +11.000ft with no RC or wifi loss, all crispy clear !
No boosters ( not even the special app ).
I did do the RTH because i was more then happy with it and i chickened due to that faulty battery from yesterday ghosted true my mind.
I made one mistake though.
On its return it did break up RC.
I placed the skew planar antenna that point downwards on the back. It had to be in front because when its fighting on its limits and you don't have control on the way back then **** can happen when the only way you can make it is in ATTI or even GPS.
GPS mode is way faster the RTH mode.
So i have to look into that, but for long range i have made 2 helicals ( 10 turn ) for the RC on the bird as well so i guess i have to stick with that. But i wanted to see the range of the skew planar antenna's and the wifi helical on the pilot side and how well they worked together.
Its also wise to consider the wavelength and the length of the coax. I didn't take it into account but i have to know better as a HAM radio guy.
Anyway i had the birds 2 x RC u-fl connectors removed by scraping with a hobby knife easy and gently away the concrete like glue.
I toke the coax cables and made then to fit the size i needed and soldered the rp-sma connectors myself.
But as mentioned i didn't take in account the length of it.