so ive been running a 5/8 wave mag mount on the truck for years and it works fine for hitting the two main repeaters in town but theres one about 40 miles out i can barely scratch on a good day, maybe S1 into the machine and sometimes it just doesnt open the squelch at all. been thinking about swapping to either a longer collinear or maybe a small 3 element yagi on a bracket off the side of the cab but im not sure if its actually worth messing with a directional antenna when im moving around.

the repeater im trying to hit is roughly northeast of where i drive most days which is kind of convenient but obviously not always. anyone actually run a yagi on a mobile install? seems like itd be a pain to aim while driving and i guess you wouldnt really aim it at all, just point it the direction you usually travel and hope for the best. or maybe the gain from a longer collinear would just solve this without the directional headache. the Diamond NR770HB has been on my radar for a while, gain is supposed to be pretty decent for an omni.

also wondering if its a feedline issue, i have about 12 feet of whatever coax came with the mag mount which is probably garbage but i dont know what loss im actually seeing there. maybe thats the low hanging fruit before i go buying new antennas.

the coax is almost certainly part of your problem. those stock cables that ship with mag mounts are usually RG-58 or something even worse with cheap connectors, and at 2m you can easily lose a dB or two in 12 feet depending on how bad it is. id start there honestly, grab some LMR-240 or even just decent RG-8X and put on proper connectors and see how much difference that makes before spending money on a new antenna.

that said the NR770HB is a solid antenna and would be an upgrade over a basic 5/8. yagi on a mobile is kind of a pain unless you have a specific reason for it, most people doing mobile VHF work just want a good omni and better feedline. if you were doing like a specific trail or route where you knew the repeater was always behind you or something maybe a yagi bracket makes sense but for general driving around i wouldnt bother.

yeah i had almost this exact situation a couple years back trying to hit a machine about 35 miles out and it turned out my PL tone was slightly off too which wasnt helping, so worth double checking that if you havent. but assuming thats fine, the feedline thing is real. i replaced the stock mag mount coax with some LMR-195 i had laying around and noticed a difference on receive at least.

i briefly tried a 5 element yagi on a bracket on a long trip out west where i was following basically one highway the whole time and just pointed it forward. it was kind of funny because it actually worked pretty well for that specific use case, picked up a repeater maybe 60 miles out i would never have heard otherwise. but as a general solution for everyday driving its pretty impractical, you'd spend more time thinking about antenna direction than actually talking. stick with a better omni id say.