ok so ive been running a mag loop on my desk for about 8 months and honestly its fine for what it is but i want to actually build something real. the plan is a center fed dipole for 40m, probably inverted V because i only have one decent high point (a big oak tree in the back, maybe 35 feet up at the apex). i have a spool of 14 AWG stranded copper wire and some coax laying around.

the thing i keep going back and forth on is the feedpoint. ive read like 6 different articles and half of them say just connect the coax directly and use a 1:1 choke balun, the other half act like youll burn your rig down without a 4:1. my understanding is a dipole in free space is like 73 ohms so a 1:1 should be fine, but when you fold it into an inverted V the impedance drops a bit depending on the angle... is that right? or am i misremembering that.

also do i really need to stress about wire length to the half inch or is the standard formula (468 / freq in MHz) close enough to tune from? im planning to cut long and trim, which seems obvious but i just want to make sure im not missing something dumb before i go buy connectors and whatever else i need.

you've basically got it right on the impedance thing. a flat dipole at a decent height over real ground is close enough to 50 ohms that a direct coax feed works, and a 1:1 choke balun is mostly there to keep RF off the coax shield rather than do any impedance transformation. the 4:1 crowd isnt wrong exactly, they're usually thinking about a folded dipole or running it multiband and accepting a higher SWR, but for a simple 40m dipole you don't need it.

inverted V does drop the impedance a bit yep, more so if the angle is shallow. at like 120 degrees included angle you're still in the ballpark, closer to 50-60 ohms depending. not gonna matter with modern transceivers and their built-in tuners. cut it long like you said, just leave yourself 6 inches or more on each leg because trimming is way easier than splicing back in wire if you overshoot.

468 is fine as a starting point. wrap the ends, hang it up, check SWR across the band, then trim in small increments. the feedpoint height and what's around the antenna changes things anyway so you can't really pre-calculate it exactly.

yeah cut long and trim is definitely the move, i cut one to exactly calculated length my first time and it resonated about 40khz high and i had to splice in more wire which was a pain. also if you're using stranded wire the velocity factor is essentially 1.0 so the formula works fine, some people get confused because they think wire has a VF like coax does.

one thing i'd add -- wind a few turns of the coax on a piece of PVC pipe right at the feedpoint if you dont have a proper balun. it's not perfect but it knocks down common mode current enough to make a noticeable difference. i did this on my first 20m dipole and it worked fine for over a year before i bothered building a proper choke balun.