so i've been running an end-fed halfwave for about two years now and honestly it's been fine but ive always wanted to try a proper dipole setup. anyway last weekend i finally got around to putting up a fan dipole, three elements fed from a single SO-239 at the center. got it up about 35 feet which i know isnt ideal but its what the trees allow me to work with.

the 40m element is working great, SWR is right around 1.4:1 which im pretty happy with. the 20m element though is reading higher than i expected, sitting around 2.1:1 and the 15m is actually the worst one at closer to 2.8:1. i spread the elements at roughly 15 degrees from each other and i figured there would be some interaction but wasnt expecting the higher bands to be this fussy. did i space them too close? ive read that keeping them at least 6 inches apart at the feed point helps but honestly im not sure i achieved that cleanly with the way i built the center insulator.

also the thing tends to resonate a bit low on 20m, like maybe 200khz below where i want it which makes sense since the elements are drooping a bit at the ends where they go over the branches. just wondering if anyone else has dealt with this and whether it's worth cutting them back a bit or just throw a tuner at it.

the element interaction on fan dipoles is real and 15 degrees is probably a bit tight for 3 elements honestly. i built one a few years ago and ended up spreading them closer to 20-22 degrees and things cleaned up quite a bit on the higher bands. the problem is each element kind of sees the others as part of the antenna especially when theyre that close at the feedpoint and it shifts the resonant frequency around.

for the 20m being low - yeah drooping ends will do that, its effectively making the element electrically longer. you could trim a few inches off and see what happens or if youre not trying to compete in contests or anything just run a tuner and call it done. honestly 2.1:1 isnt terrible, most rigs will handle that fine without melting anything.

im in a similar situation with my fan dipole, 40 and 20 only though. one thing that helped me was making sure the wires weren't twisting around each other near the feedpoint, sounds obvious but i had a section where they were almost touching for about a foot and it was making the swr on 20 really weird. once i separated them properly and used some small plastic spacers it settled down a lot. might be worth having a look at that before you start cutting wire.