so ive been licensed for about 8 months now and been using a buddistick which works ok but i want to build something more permanent for 40m. been reading everything i can find about half wave dipoles and i think i get the basic math, 468 divided by freq in mhz, so for 7.150 thats roughly 65.5 feet total, each leg about 32.75 feet. seems straightforward enough.

my question is more about the feedpoint. im planning to use 50 ohm coax to the shack and i keep reading about how the impedance at the feedpoint of a dipole is around 73 ohms so theres a slight mismatch but most people just deal with it and the swr is still low enough that a modern radio wont freak out. is that right? or do i need a balun at the feedpoint, and if so what kind. ive seen people say 1:1 current balun, some say voltage balun, some say just choke the coax with some ferrite beads and call it a day.

also planning to hang it in an inverted V config because i only have one good tall support (a pine tree thats maybe 40 feet up). the ends would only be about 8-10 feet off the ground. is that gonna be a problem for the radiation pattern or should i just not overthink it and try it

the math youre doing is fine, though cut a little long and trim to resonance — that formula is just a starting point and your local environment will affect the actual resonant length. always easier to trim than to add wire back on.

on the balun question, honestly for a first dipole just wind yourself a simple choke balun, like 8-10 turns of the coax in a coil maybe 6 inches diameter at the feedpoint, or if you have some mix 31 ferrite toroids those work great. a proper 1:1 current balun is better long term but the coax choke will get you on the air and help keep RF off the feedline which is really what youre trying to prevent anyway. the voltage vs current balun debate gets religious real fast, dont go down that rabbit hole yet.

inverted V is totally fine, probably better than a flat top at your height honestly since the lower angle of radiation on 40 can actually work in your favor. 8-10 feet on the ends isnt ideal but its workable. just make sure nothing is touching the wire and youll be fine. get it up and tune it, worst case you adjust.

yeah the inverted V will work, i ran one for two years with the ends like 6 feet off the ground and worked plenty of dx on 40 so dont stress it too much. the feedpoint height matters more than the ends.

one thing i will say — get yourself a cheap antenna analyzer before you cut anything if you can. even one of those little nano vna units, they're like 40 bucks now and it takes all the guesswork out. way easier than the old trial and error method of transmit, check swr, trim, repeat.