@abcd567 the description for the V-stub picture says “Physical Build - Prototype” - did you ever make any additional modifications to go from “prototype” to “final”?
Do you have any guidance on how to “tune” it? I presume you were using the analyzer in the photo to tweak the length to minimize the VSWR. Once you had a length, did you solder it - or make any permanent setting?
I don’t have a VNA, but have pondered getting one - is there way to tune this effectively without one?
Would setting the upper length to 150mm and calling it a day work “reasonably well” do you think? At least resulting in better performance than a 1/4 wave/ground plane spider?
Looking back at a post you made in 2018 here:
It looks like the “1/4 wave spider with ground plane” was giving 1.31dB, so the V-Stub ought to boost performance by ~3dB relative to it. That seems enough to warrant my giving it a try to construct one - even if I can’t optimally tune it.