so ive been putting this off for about a year and finally just built a simple 40m dipole out of some 14 gauge stranded wire i had laying around in the garage. center insulator is just a piece of PVC i drilled holes through and fed some paracord through, nothing fancy. coax goes straight down to the shack from there.

the thing actually works which is exciting but my SWR is doing something strange. at the low end of 40m around 7.000 it reads like 1.8:1 which is fine, but as i go up toward 7.300 it climbs to almost 3:1. i cut it to the standard formula, 468/f and used 7.150 as my target. legs are each about 33 feet.

is this normal for a dipole or did i mess something up with the feedpoint. im feeding it with about 50 feet of RG-8X if that matters. the coax just hangs down at kind of an angle, not straight down.

yeah that SWR curve behavior is pretty typical for a resonant dipole honestly, youre seeing the impedance change as you move away from resonance and with 40m being 300khz wide that swing isnt terrible. the 3:1 at the high end is a little steep but most rigs and tuners handle that just fine.

one thing that might be throwing it off is how the coax leaves the feedpoint. if its running parallel to the antenna for any length before dropping down you can get some common mode current on the braid and that basically makes part of the coax act like part of the antenna. a simple choke balun right at the feedpoint, even just coiling a few turns of coax, can clean that up a lot and usually helps the SWR curve behave more symmetrically. worth trying before you start trimming wire.

what height is it at? that changes things more than people realize. if its close to the ground youre going to see the resonant point shift down and the curve gets kind of squished. i had mine at about 20 feet once and the SWR was all over the place compared to when i got it up to 35.