so i finally got around to building a basic half wave dipole for 40m, been meaning to do this forever. used 14 gauge stranded wire i had laying around in the garage, cut each leg to roughly 33.5 feet based on the 468/f formula. fed it with some RG-8X i had leftover from a previous project, center insulator is just a piece of PVC i drilled out and zip tied together which honestly looks janky but seemed solid enough.

hooked up my analyzer and the resonant point is sitting somewhere around 6.9 MHz instead of 7.150 where i was aiming. SWR at 7.150 is reading about 2.4:1 which isnt terrible but i wanted to get it closer. the antenna is in an inverted-V config, apex is maybe 30 feet up on a tree, legs drooping down to about 8 feet at the ends. i havent trimmed anything yet because i was expecting to need to add length not take it away.

is the low resonant frequency from the inverted-V configuration pulling it down? i know the angle of the legs affects things but i wasnt sure by how much. or is stranded wire just electrically longer than solid? ive read both things in different places and now im confused. any input appreciated, this is my first scratch build so im probably missing something obvious.

yeah the inverted-V geometry definitely does that, the closer the legs are to horizontal the more the resonant frequency shifts down compared to a flat top. at 8 feet off the ground for your ends you're getting a pretty steep angle and that'll make the antenna behave electrically longer than the formula predicts. stranded wire also has a tiny bit of effect compared to solid but honestly that's minor, the geometry is the bigger factor here.

the fix is just trimming. start taking small amounts off each end, like 2-3 inches at a time, check the analyzer, repeat. annoying but it doesn't take that long. also worth double checking your coax connection at the center - a bad solder joint or a little moisture in there can do weird things to your readings. 2.4:1 at your target frequency isnt the end of the world for 40m but you can definitely get it under 1.5 with some fiddling. what center insulator material did you say you used?

im in almost the exact same situation lol, built a 40m dipole last spring and spent like three weekends trimming and repositioning before i got it where i wanted. one thing nobody told me was that the height above ground really changes things too, when i raised mine from 25 feet to around 35 the resonant point shifted noticeably. so if you ever get a chance to get that apex higher it might change your readings again anyway. just something to keep in mind before you trim too aggressively.