so i've been putting this off for months but finally sat down last weekend and built a simple center-fed dipole for 40m. used some 14 gauge stranded copper wire i had laying around from an old extension cord project, grabbed a SO-239 chassis connector from the junk box and made a basic center insulator out of a piece of cutting board i cut up. yeah i know that sounds janky but it seems to work fine so far.

cut each leg to about 33.5 feet based on the 468/f formula and got an SWR of around 1.8:1 at 7.150 which honestly surprised me, i was expecting worse. ran about 35 feet of RG-8X down to the shack. no balun right now which i know is probably not ideal but i wanted to get it up first and tune from there.

my question is really about feedpoint impedance — im getting some RF on the outside of the coax (coax shield gets warm after a few minutes on SSB) and i know thats a balun issue but im wondering if anyone has just wound a choke balun right at the feedpoint vs using a ferrite bead balun or whatever. also the antenna is in kind of an inverted-V config, apex at about 30 feet, legs sloping down to about 8 feet at the ends. does that change the feedpoint Z much compared to a flat dipole? ive read all kinds of different things on this.

yeah the inverted-V does change the impedance a bit, somewhere around 50 ohms or a touch lower depending on the included angle of the legs. if your legs are sloping pretty steeply the Z can drop noticeably. with the apex at 30 and ends at 8 feet over what kind of span horizontally? that matters a lot for figuring out the angle. if youre closer to 90 degrees between the legs you're probably still in decent shape, more like 120 degrees and the Z starts to creep up a bit.

on the choke balun question, i've done both and honestly for a simple 40m dipole a few turns of coax wound through a ferrite toroid works great and its compact. i usually do 8-10 turns through a mix 31 or mix 43 core right at the feedpoint. the 1:1 choke just keeps the common mode off the feedline and it makes a real difference. you can also do the air-wound coax choke (like 8 turns in about a 6 inch diameter coil) taped right there at the center insulator and thats worked fine for me on 40 and 80. simpler to build if you dont have toroids handy.

cutting board center insulator is actually pretty solid, i did the same thing with some HDPE sheet i had. holds up fine in rain. just make sure you drill the wire holes and seal them somehow if you're worried about moisture wicking in over time, though honestly its probably fine.

the warm coax thing is definitely the common mode current and a choke will fix it. i wouldnt stress about winding a fancy balun just yet, even just coiling up maybe 10 feet of the feedline into a loose coil right below the feedpoint can help knock it down enough to get you on the air cleanly while you figure out something more permanent. its not a great long term fix but it at least confirms whether the balun is whats causing your issue before you go building stuff.