so i finally got around to building a dipole instead of just complaining about my vertical not working on 40m. cut two legs to about 33.5 feet each for 40m resonance, used some old 14 gauge stranded wire i had laying around from an electrical project, fed it with RG-8X through a choke balun i wound myself on a piece of PVC using a mix of turns i found on some random webpage (probably not ideal).

got it up in kind of an inverted V config with the apex at about 30 feet off the ground, ends are maybe 8 feet up tied to some fence posts. SWR is sitting around 1.4:1 at 7.150 which honestly surprised me, thought itd be way off. but i cant figure out why its reading higher on the low end of the band, like around 7.020 its closer to 2.1:1. shouldnt it be lower SWR down there if the antenna is cut a little long? or did i mess up my math somewhere. the legs might not be exactly equal length, i measured but the wire stretches a little when tensioned.

also using a cheap nano VNA to check, not sure how much i trust it but it seems consistent at least

the SWR being higher at the low end of the band is actually telling you the antenna is resonant above where you want it, not below. if 7.150 is your sweet spot and 7.020 is worse, that means your antenna is tuned a bit high. you'd want to add a little length to both legs to pull resonance down. try maybe half an inch to an inch on each side and remeasure, its tedious but thats just how it goes with wire antennas.

the nano VNA is fine for this kind of work, dont let people tell you its garbage. its not a $3000 Rohde but for checking resonance on HF it does the job. the choke balun situation -- if you dont know how many turns and what core you used its hard to say if its actually doing anything, but if your SWR looks clean and youre not seeing common mode weirdness it might be okay. id revisit that later once youre happy with the resonance point.

yeah what he said about the length. also 8 feet for the ends is pretty low, close to ground like that can really pull the resonant freq down and mess with the feedpoint impedance too. if you can get those ends up higher even to like 12-15 feet you might see it shift and the pattern will be a lot cleaner. i built a similar inverted V last summer with the ends barely off the ground and it was a pain to get right, kept interacting with the fence