so i finally decided to stop being lazy and just build a dipole instead of buying one, figured how hard can it really be. grabbed some 14 gauge solid copper wire from the hardware store, cut both legs to about 16.5 feet each for 40m, and hooked it up with a SO-239 chassis connector i had in the junk box. center support is just a piece of PVC i drilled holes through, nothing fancy.

got it up about 25 feet in an inverted V config tied off to my garage peak and two trees. fed it with maybe 50 feet of RG-8X i had lying around. here's the problem though — SWR at 7.150 is reading like 3.2:1 on my meter. i expected it to be a little off but not that much. trimmed maybe 4 inches off each leg and its now sitting around 2.8:1 which is better but still way off from what i thought i'd get. resonance seems to be wandering around too, like it changes depending on the weather almost.

not sure if its the feedline, the connections at the center piece, or if i just screwed up the length calculation somehow. using the 468/f formula which i thought was standard. anyone dealt with this building from scratch or have i just made some dumb mistake somewhere

the inverted V configuration does change things a bit from a flat dipole — the legs being angled down effectively shortens the electrical length so you usually need to add a bit back rather than trim. a lot of guys forget that part. also 14 gauge solid copper is fine but double check your connections at the center insulator because a cold solder joint or a bad crimp there will wreck your readings and yes it can absolutely shift with temperature and humidity if theres any exposed connection.

the weather sensitivity you mentioned is a red flag honestly. a properly sealed feedpoint shouldnt care much about weather. i'd resolder everything with good rosin core solder, heatshrink over it or at minimum use self amalgamating tape wrapped tight, and then recheck. also make sure your feedline isnt running parallel to the antenna legs for any significant length — that can couple into the antenna and mess with the pattern and your SWR reading both.

yeah what he said about the inverted V, i had the same problem on my first build and kept trimming and trimming and making it worse lol. also depending on how close your antenna is to the garage roof the capacitive loading from that can pull resonance down too. 25 feet isnt a ton of height for 40m, more height would probably help clean things up. dont give up on it though, even at 3:1 most tuners will handle it fine and the antenna is still radiating