so i finally got around to building a proper 40m dipole instead of using that random wire i had strung up for the past two years. cut it to the standard 468/f formula which came out to about 66 feet total, used some 14awg stranded wire i had laying around from an old project and a SO-239 chassis connector in a little weatherproof project box for the center insulator.

got it up in an inverted-v configuration with the apex at about 30 feet off the ground using my push-up mast. the legs are drooping down to about 8 feet at each end tied off to some trees. SWR at resonance is sitting around 1.4:1 which honestly isnt bad but i trimmed the ends and now its resonant at like 7.150 which is fine for my purposes.

my question is about height though. everything i read says you want a half wavelength up for a dipole at 40m which is like 66 feet, which obviously i dont have. am i losing a lot by being at 30 feet? like is it worth trying to get a taller center support somehow or is the inverted-v at 30 feet still reasonably usable for making contacts and not embarassing myself on the band

30 feet on 40 is totally workable, dont stress about it too much. yeah you're not going to have the low angle radiation pattern that would help with dx but for general ragchewing and even some decent dx on good nights it'll do fine. i ran an inverted-v with the apex at 25 feet for about three years and worked a bunch of europe and japan on it, granted conditions were better back then but still.

the inverted-v shape actually helps a bit by bringing the current maximum up higher relative to a flat-top at the same apex height, so its not as bad as it sounds. the bigger thing im thinking is your 1.4:1 after trimming — that's pretty decent but make sure you're measuring that at the radio end with the feedline included because sometimes the coax length can do weird things to what you're seeing at the rig versus what's actually at the feedpoint. if you have a way to measure at the feedpoint directly that'd confirm it's actually resonant where you think it is.

yeah what he said. i built basically the same antenna last spring and 30 feet works fine. i used a 1:1 choke balun at the feedpoint too which might be worth adding if you havent, keeps rf off the coax shield. made a noticeable difference for me on receive anyway, less noise.