so ive been putting off building my own antennas for ages because i always figured id mess it up, but finally got tired of paying for stuff i could probably make myself so i cut a half wave dipole for 40m last weekend. used the 468/f formula, ended up with two legs of about 33.3 feet each, solid 14 gauge copper wire i had left over from some house wiring, fed it with RG-8X i already had lying around.

hung it up in an inverted V config off my chimney, apex is maybe 28 feet up and the ends droop down to about 8 feet off the ground. used a cheap PL-259 connector i soldered on myself, which honestly might be where things went sideways because my soldering has always been kinda mediocre.

problem is the SWR at resonance is sitting around 2.1:1 and the resonant point is way down around 6.8 MHz, not where i wanted it at all. i trimmed a little off each leg and it came up to 7.0 MHz but SWR barely moved. antenna analyzer is an old MFJ-259 that i borrowed from the club. the feedpoint is just the center insulator i made out of a piece of PVC, twisted the two wires through holes and soldered to the coax center and shield.

not sure if this is a feedpoint impedance issue or if the inverted V angle is doing something weird or if my PL-259 is just garbage. any thoughts would be appreciated, been scratching my head on this for a few days now

the inverted V will definitely shift resonance lower compared to a flat top, the coupling between the drooping legs changes things. 28 feet at the apex with ends at 8 feet is a pretty steep angle — if you measure the angle between the legs it's probably under 90 degrees which compresses the radiation resistance too, that could explain the 2.1:1 even at resonance since youre looking at maybe 35-40 ohms instead of the usual 50-ish for a flat dipole.

honestly though 2.1:1 isnt catastrophic, most rigs will handle that fine. the bigger issue is getting it to the right frequency. trim carefully, like 3-4 inches per leg at a time and recheck. also double check that coax isnt laying on the ground right at the feedpoint because that can really mess with your readings on the 259. the common mode current thing is real and if you dont have a choke balun or at least some ferrite beads on the coax near the feedpoint the coax shield is basically acting like part of the antenna and youll chase your tail forever.

yeah what he said about the balun, i built probably four or five dipoles before someone finally told me about common mode and suddenly everything started making a lot more sense. i wind mine on a piece of PVC with about 8-10 turns of the coax itself right at the feedpoint, works well enough for casual use even if its not a proper 1:1 choke balun.

also your house wiring copper, is it solid or stranded? solid should be fine but just checking. one other thing — 14 gauge is kinda stiff and heavy, not a problem electrically but if your center insulator is just twisted wire through PVC holes it might be putting mechanical stress on the connection and that solder joint could be intermittent. had that happen to me once and it drove me crazy troubleshooting it