so ive been going back and forth on this for a while now and figured id just ask here because googling it gives me nothing but product pages. we have a 70cm link antenna up on a hilltop site, currently running a comet GP-9 or whatever the 70cm version is called, its been up there maybe 4 years and works fine but the path to the far repeater is kind of marginal. maybe 2-3 db of headroom on a good day.

someone suggested swapping to a yagi pointed at the far site and just eating the loss of omnidirectional coverage since the link only needs to talk to one place anyway. which makes sense on paper. but then someone else said the wind loading up there is already sketchy and a yagi pointed at something 40 miles out would need to be rock solid or the whole thing falls apart every time it gets gusty.

the mast is a 10 foot piece of 1.5 inch steel pipe, guyed at the top, its not going anywhere but i dont know how a horizontal yagi would handle sustained 40-50 mph winds which we do get up there in winter. anybody run a long boom yagi on a hilltop site in rough weather and lived to tell about it

yeah we had almost exactly this situation on a 2m link a few years back. ended up going with a 9 element yagi, M2 i think, and the wind thing was a real concern. what we did was mount it on a short stub boom with a thrust bearing so if it really started flexing it wouldnt torque the mast fitting. honestly it held up better than expected. the element count matters less than how solid the mounting is -- i've seen 5 element yagis shake loose in moderate wind because someone just clamped it to the mast with a single u-bolt and called it done.

on the db question, you'd pick up whatever the GP-9 was giving you in gain (probably 8-9 dbi or so) plus all of that gain focused on one direction so youre potentially looking at 12-14 db improvement on that path. that should fix your margin problem pretty decisively. just make sure your coax run gets resealed when you swap it, up there moisture is the killer not wind in my experience.

40-50mph is not that bad for a yagi if its mounted right tbh. ive seen people worry way too much about that. the real issue is ice loading, if you get icing up there a long boom yagi can get absolutely hammered. colinears handle ice a bit better just due to their profile. something to think about depending on your climate.