so i finally decided to stop being lazy and build a proper dipole instead of using that trapped vertical i borrowed from a buddy. picked up some 14 gauge stranded wire from home depot, grabbed a center insulator i had in a junk box, and cut the legs to half wavelength for 40m. the math put me at about 33 feet per side which i know is a bit long but i wanted to trim to resonance.

heres the thing though — when i put the antenna analyzer on it the SWR null is sitting around 6.8 MHz instead of where i want it which is somewhere around 7.150 or so. i was expecting it to be a bit long but this seems way off. the wire is just hanging as an inverted V with the apex at about 30 feet, ends maybe 8 feet off the ground. i used RG-8X for the feedline and its a fairly short run, maybe 40 feet to the shack.

did i mess up the math or is the inverted V configuration changing the resonant frequency that much? i read somewhere the angle of the legs affects things but i cant find a straight answer on how much. also should i be using solid wire instead of stranded? a guy at the club said stranded doesnt matter but another guy said it does and now im confused.

the inverted V geometry definitely pulls the resonant frequency down compared to a flat top dipole, the closer the ends are to the ground the more pronounced it gets. with your ends at 8 feet youre getting significant ground interaction which effectively electrically lengthens the antenna. its not unusual to see it resonate 200-400 kHz lower than calculated depending on the angle and soil conditions under it. just start trimming a few inches at a time off each leg equally, recheck with the analyzer, repeat. tedious but thats just how it goes with wire antennas.

stranded vs solid doesnt really matter for HF, that guys advice was fine. the velocity factor difference is negligible at those frequencies and the flexibility of stranded is usually worth it for a wire antenna that goes up and comes down a lot. solid is fine too if thats what you have. just trim and get it where you want it.

yeah i had the exact same thing happen with my 40m dipole last spring. kept second guessing myself thinking i measured wrong or something but it was just the inverted V thing. my ends were probably around 10 feet off the ground and it came in low too. ended up trimming maybe 18 inches total off both legs before it landed where i wanted it. just go slow with the trimming because obviously you cant put wire back on lol