so ive been running a Diamond X50 on the roof for about two years now and it works fine for hitting the local 2m repeater, no complaints really. but theres a 70cm machine about 40 miles out that i can only barely reach on a good day, like when the atmosphere is doing something cooperative. been thinking about throwing up a small yagi pointed that direction just for that one repeater but im not sure if its actually worth the effort vs just sticking with the omni.

the thing is i do use the X50 for scanning and hitting a couple other local machines too so if i swap it out i lose that flexibility. was thinking maybe a second feedline and a switch but my mast situation is kind of a mess already. anyone gone down this road? is a 5 or 7 element yagi on 70cm going to make a meaningful difference at that range or am i chasing something thats just marginal anyway due to terrain

yeah a 7 element on 70cm will absolutely make a difference over an omni at 40 miles, youre talking maybe 10-11 dBd of gain vs whatever the X50 gives you on 440 which i think is like 6.5 dBi or somewhere in that neighborhood. so youre picking up real signal, not just a couple db. the question is whether the path is actually workable at all — if theres a ridge in the way no amount of antenna is going to fix that.

the dual feedline and coax switch approach is the right call if you want to keep the omni for local stuff. i ran a similar setup for a while with an M2 on 70cm and a vertical for 2m, had a cheap relay switch box and it worked fine. just keep the feedlines short and use decent coax, LMR400 or equivalent, because 70cm really punishes you on loss especially if the run is long.

I went through almost this exact thing last spring. ended up putting a cheap 8 element yagi from a well known online seller up alongside my existing vertical and honestly the difference to a repeater about 35 miles away was night and day. went from getting into it maybe 60% of the time to pretty much solid. the coax switch thing works but i just leave the yagi connected most of the time because that repeater is the one i actually care about. the local stuff i can hit with 5 watts on a HT anyway so the omni kind of became redundant for me. your situation might be different though depending on how spread out your local activity is.