so ive been doing a lot of SOTA and general hilltop stuff lately and my rubber duck situation is obviously not cutting it anymore, no surprise there. i had a 2m yagi i built like 10 years ago from an ARRL handbook design but it got destroyed in a move and i never replaced it. been thinking about either building something new or just buying one of those cheap tape measure yagis everyone seems to love for fox hunts and portable work.

the thing is i want something that also does 70cm so i'm not dragging two antennas up a hill. the dual band yagis i've seen online look a little sketchy in terms of how the elements interact — like, does the 70cm performance actually suffer much when you add it to a 2m design? or is this one of those things where its fine in practice even if the theory looks messy. i've modeled a few things in EZNEC but i'm not confident im setting it up right for dual band stuff.

also open to hearing if anyone just uses a collinear for portable work instead. i know the gain pattern is totally different but maybe for general operating its more practical than a directional antenna you have to aim all the time

built a tape measure yagi a few years back for 2m and it works great but honestly for dual band portable i just gave up trying to make one antenna do both. what i do now is bring a slim jim rolled up in my pack for 2m when i want omnidirectional and then a little 3 element 70cm yagi i made from some aluminum arrow shafts — total weight is nothing and setup takes maybe 2 minutes. two antennas sounds like more hassle but in practice its way easier than fighting with a compromised dual band design.

if you really want one antenna though the Ed Fong dual band jpole that everyone talks about is actually pretty decent for portable, not a yagi obviously but its lightweight and the pattern is fine for most hilltop operating where you're not trying to nail a specific direction anyway. the gain isnt going to wow you but its way better than a rubber duck

yeah the interaction between elements on a dual band yagi is real and its not just a modeling thing, you can actually see it in the SWR. i built one based on a design i found on a german amateur radio site — cant remember the callsign of the guy now — and the 70cm pattern was noticeably squirrely compared to a dedicated 3el 70cm yagi i tested alongside it. still useable but if you're trying to work weak signal stuff on 70cm you'd notice. for SOTA contacts on FM repeaters and simplex it probably doesnt matter much though