so i finally got around to building a dipole for 40m after years of just using a random wire thrown over a tree. cut it to the standard 468/f formula which put me at about 66 feet total, using some 14 gauge stranded wire i had lying around from an old extension cord project (stripped it obviously). fed it with 50 ohm coax at the center with a SO-239 chassis connector i had in my junk box.

anyway the swr at 7.150 is pretty good, like 1.4:1 which i can live with. but down at 7.025 it climbs to almost 2.8:1 and my tuner handles it fine but i wanted to understand why. the antenna is about 25 feet up, inverted v configuration, legs drooping down at maybe 120 degree angle between them. i read somewhere the inverted v affects things but wasnt sure how much. should i just trim or lengthen from here or is there something else going on

inverted v vs flat top makes a real difference in resonant frequency, the drooping legs effectively make the electrical length longer than a flat dipole at the same height so your antenna is resonating lower than you aimed for. thats why 7.025 is showing high SWR — you're probably resonant somewhere below the band honestly. try trimming a few inches off each leg at a time and recheck, go slow because you cant put wire back once its cut. also 120 degrees is a pretty shallow angle, ideally you want closer to 90-120 with 120 being ok but the shallower it gets the more it behaves like a vertical which changes the whole radiation pattern situation. anyway youre not far off, should be an easy fix.

yeah what he said about the inverted v. i had the exact same problem with my first 40m build a couple years ago, kept chasing my tail with the tuner when the fix was just snipping a bit off each side. one thing i'll add — extension cord wire works fine but the insulation on some of that stuff can mess with your velocity factor slightly especially if the wire is running close to a tree branch or touching anything. probably minor but worth knowing. my current 40m dipole is just speaker wire from the hardware store, two runs of 18 gauge, works fine.