so i finally got around to building a proper 40m dipole instead of using that crappy random wire ive had strung up forever. used 14 gauge stranded copper from the hardware store, center insulator i made from a piece of cutting board (yeah really), and just ran coax down to the shack. fed it at about 30 feet with a slight inverted-v droop on each side.

the thing is the SWR across the band is fine on the low end, like 1.4:1 around 7.050 which is where i want it, but when i sweep up toward 7.250 or so it shoots up to almost 3:1. i get that SWR changes across the band but something feels off. the two legs should be equal, i measured twice before cutting. each side is about 33.3 feet. i dont have an antenna analyzer yet, just using the radio's built in SWR meter which i know isnt ideal.

wondering if anyone else has seen this with a basic dipole or if im missing something obvious. the feed point connection looks solid, i soldered everything and taped it up with self amalgamating tape.

33.3 feet per side sounds close but honestly the thing to check first is whether the coax braid is acting as part of the antenna. without a choke or balun at the feedpoint the common mode current on the outside of the coax can do all kinds of weird stuff to your pattern and SWR. a lot of guys just wrap 8-10 turns of coax into a coil at the feedpoint and tape it off, acts as a decent choke balun. might not fix everything but its usually the first thing to rule out.

also 3:1 at the high end of 40m on a dipole cut for the low end isnt that surprising honestly. the band is pretty wide and a half wave resonant antenna is going to have higher SWR away from resonance. if your rig can handle 3:1 or you have a tuner you might just leave it.

cutting board insulators are actually totally fine, ive used them for years. what kind of coax are you running and how long is the feedline? sometimes the line length can make the SWR reading at the radio look worse or better than it actually is at the antenna. a half wave of coax at the operating frequency will show you the true impedance, any other length and youre reading through a transformer basically. not that it matters for actual operation usually but it can make troubleshooting confusing if you dont account for it.