so ive been going back and forth on this for a while now and figured id just ask here because the repeater group i'm in cant seem to agree on anything. we've got a link site about 8 miles from the main repeater, sits on a pretty decent hilltop, maybe 200ft above average terrain in that direction. right now theres a vertical collinear up there — think its an old comet GP-9 or something close to it, been there for years — and the link is marginal at best. drops out when the weather gets weird and honestly even on good days the audio isnt great.

someone in the group wants to put up a yagi pointed at the main site and be done with it, which honestly makes sense to me since its a fixed point to point path. but someone else is saying we lose the ability to hit the repeater from mobile units in the area if we go directional. my thought is that's not really what the link antenna is supposed to do anyway, that's the repeater's job. am i wrong here?

the path isnt super long so i dont think we need massive gain, maybe a 5 or 6 element on 2m would be more than enough. just wondering if anyone has done something similar and whether its actually worth climbing the tower twice to swap things out or if theres some middle ground antenna im not thinking of.

you're not wrong about the link antenna's job — if its a dedicated point to point path then a yagi just makes sense, full stop. a collinear on a link site is kind of doing the worst of both worlds, you get some gain but its all going out horizontally in directions you dont need and youre picking up noise from those same directions too. a 6 element on 2m is going to give you somewhere around 10dBd depending on the design and boom length, which is a massive improvement over a GP-9 on a path that's already marginal.

the guy worried about mobiles hitting the link antenna is confused about how the system works, like you said. mobiles work the repeater, the repeater works the link, thats the whole point. unless you have some weird hybrid setup where people are supposed to hit the link directly which would be strange.

one thing id think about is polarization — if your main repeater is running vertical you want your link yagis to match on both ends, seems obvious but ive seen people mix it up and wonder why they're losing 20db. also worth doing a proper path calc in something like Radio Mobile before climbing anything, might find you dont even need the yagi and the real problem is feedline or a corroded connector somewhere on that old comet.

yeah we had almost the exact same argument at our club a few years back, different hilltop same basic problem. ended up going with a pair of M2 2M5WL yagis on the link and it was night and day difference, like the path went from unreliable to basically rock solid. the antenna isnt even that big, fits on a pushup mast no problem.

only thing id add is dont cheap out on the feedline for the link end especially if theres any real run from the antenna to the radio. we used LMR-400 and i think it was worth every penny. someone wanted to reuse the old RG-8X that was already on the tower and i'm glad we talked them out of it.