so ive been running a trapped vertical for a few years now and honestly it was fine but i always felt like i was leaving something on the table, especially on 40 where it just never seemed to perform as well as guys running dipoles. anyway i finally had a free weekend and put up a fan dipole — three separate dipoles all fed from the same feedpoint, cut for 40, 20, and 15 meters. ran about 60 feet of RG-8X down to the shack.

the interaction between the elements is definitely a real thing you have to deal with. my 40m legs came in a bit long after i put the other elements up, which makes sense because of coupling, so if youre doing this expect to do some trimming after everything is in the air. i ended up with the elements spread out at maybe 20-25 degrees from each other which seems to help keep the interaction manageable.

overall swr is well under 2:1 on all three bands without a tuner which is kind of amazing compared to the vertical. noise floor seems lower too which i wasnt really expecting. on 20 especially the difference is pretty noticeable, im hearing stations i would have completely missed before. havent done any serious A/B comparison but subjectively its a big improvement for basically the cost of some wire and a few hours of work.

anyone else running a fan dipole and have tips on dealing with the element interaction thing? and has anyone tried adding a 10m pair to one of these without everything going sideways?

yeah the coupling issue is real and kind of annoying the first time you run into it. what i did when i built mine was start with just the 40m dipole, get it resonant, then add 20m and retrim, then 15m last. basically build it up one band at a time instead of cutting everything to the textbook formula and hoping for the best. saved me a lot of going up and down the ladder.

on adding 10m — i tried it once and the interaction with the 15m elements was enough to mess both of them up a bit. ended up just leaving 10m off and using the tuner when i want to operate there. your mileage may vary depending on how much separation you can get between the elements physically but for me it wasnt worth the hassle. the three band version is pretty much a set it and forget it antenna which is kind of the whole point for me.

I've had a fan dipole up for about two years now, 40 and 20 only because my yard just doesn't have room for long enough supports to do the fan spread on more bands without the ends drooping down into the fence. The noise floor thing you mentioned — totally agree, it was the first thing I noticed compared to my old vertical. I'm in a pretty suburban location so any reduction in pickup of local noise makes a real difference.

One thing I'd add is that the feedpoint connection is worth spending some time on. My first attempt I just twisted the element wires together at the center insulator and taped everything up and it worked fine until some moisture got in over a winter and I started getting weird intermittent swr readings. Redid it with proper solder connections and a bit of self-amalgamating tape and havent had a problem since. Probably obvious but worth mentioning since its one of those things thats easy to half-do when youre excited to get the antenna in the air and just want to test it.