so i finally got around to building a simple 40m dipole out of some 14 gauge stranded wire i had laying around in the garage. cut each leg to roughly 33.5 feet based on the 468/f formula and fed it with some RG-8X i had left over from a previous project. center insulator is just a piece of white PVC i drilled and ran the wire through, nothing fancy.

the swr is sitting around 1.4:1 at 7.150 which honestly isnt bad for a first try but something feels off when i transmit. the signal reports im getting on 40m are decent enough but on 20m with the tuner its just... i dont know, feels like im fighting it more than i should be? the tuner gets there but it takes a while and the readings seem to jump around a bit.

antenna is up about 25 feet in an inverted-v configuration, apex tied to a tree. i used no-ox on the connections and soldered everything at the feedpoint. maybe the coax length is doing something weird? its about 67 feet of RG-8X which i think might be a half wave on some band but i cant remember if that matters for unbalanced feed or not.

anyway has anyone else had this kind of experience going from a resonant band to using a multiband tuner setup on a simple dipole? wondering if i should just cut a fan dipole instead or throw up a random wire

the coax length thing is real but its probably not your main issue here. what youre describing with the tuner jumping around sounds more like a common mode current problem to me — did you put a balun or choke at the feedpoint? without one the coax shield becomes part of your radiating system and it can make the whole thing act unpredictably, especially when you move to bands the dipole wasnt cut for. even a simple ugly balun, just coil up like 8-10 turns of the feedline in a coil about 6 inches across right at the feedpoint, can make a noticeable difference. i did basically the same build last summer and had the exact same tuner weirdness until i added a W2DU style bead choke. after that 20m settled right down.

the 1.4 on 40m is fine honestly, youre probably a bit long which would put resonance below 7.150 but thats workable. id trim maybe half an inch off each leg at a time if you want to dial it in tighter but its not worth obsessing over.

yeah fan dipoles are great but theyre also kind of a pain to keep from tangling up if youre using a tree. i went that route and ended up with 40 and 20 legs twisted together after the first windstorm. ended up just putting up a 135 foot doublet fed with ladder line into a tuner and honestly the simplicity is just better for me. works 80 through 10 without too much drama