so ive been running a diamond x50a on my roof for a couple years now and it does fine for the repeaters i use most but theres one about 45 miles out that i can hit sometimes and sometimes not, usually depends on weather i think. a buddy at the club was telling me i should just build or buy a yagi and point it at that one repeater and forget about the collinear but the thing is i also use that antenna for local stuff and monitoring the national calling freq so i dont really want to give up the omnidirectional coverage.

was thinking maybe put up a second coax run and switch between them depending on what im doing, but then i get into the whole feedline loss thing and i dont know if a yagi mounted at the same height as the x50 would actually outperform it toward that one repeater by enough to matter. the repeater is on a hilltop and im in a bit of a valley so line of sight isnt great. maybe this is more of a terrain problem than an antenna problem honestly.

anyone dealt with a similar situation, like mixing omni and directional on vhf and switching between them?

yeah the terrain is probably your bigger issue tbh. a yagi will absolutely give you more gain in the direction you point it, something like a 9 element on 2m could get you 12-13 dBd which blows the x50 out of the water gain-wise, but if youre in a valley with a ridge or hill in between you and the repeater input youre kind of fighting physics. that said ive seen cases where even a modest improvement made the difference between quieting the squelch and not, so its not hopeless.

the dual antenna with a switch setup is totally doable and a lot of guys do exactly that. just keep the coax runs as short and matched as you reasonably can, LMR-400 or equivalent, and a decent A/B coax switch at the radio isnt that expensive. honestly id try borrowing a yagi first before buying anything just to see if it even moves the needle for that path. your club probably has somebody with one you could throw on the roof for a weekend test.

i ran almost exactly this setup for a while, x50 plus an old home brew 5 el yagi i had sitting around pointed at a mountain top machine about 38 miles from me. coax switch at the operating position, worked fine. the yagi didnt completely solve my path issues but it was noticeably better, like going from marginal to solid most of the time. wasnt perfect but good enough that i kept it up there for a few years until the boom cracked in a windstorm.

one thing i will say is make sure whatever mast or mount you use for the yagi is solid because even a little movement in the wind will take you off axis and if youre already on a marginal path that can make a big difference. i used a TV antenna J-mount on the chimney and it was fine but your situation might be different.