so i've been putting off doing a proper mobile install for like two years now and finally just did it this weekend. got a Yaesu FT-7900R mounted under the dash, ran the power leads direct to the battery with the inline fuses and everything. antenna is a Tram 1185 dual band mag mount sitting on the roof for now until i can do a proper through-hole mount.

here's the thing though — SWR on 2 meters reads fine, like 1.2 or so, but on 70cm it's jumping up to almost 2.5 on some frequencies. i checked the connector and it looks okay but im not super experienced with coax terminations. the pig tail on the tram is that RG-58 type stuff which i know isnt ideal. could that be the issue or should i be looking somewhere else first? i didnt use any adapters, just straight PL-259 to the radio.

truck is a 2018 F-150 if that matters. hasn't caused any audio issues that i can tell but i want to get this sorted before i start using it more regularly.

RG-58 is definitely not your friend on 440 — the loss on that stuff at UHF is pretty significant compared to something like LMR-400 or even RG-8X. But honestly a 2.5 SWR isn't going to kill you for local repeater work, it's just not ideal. Before you go pulling new coax though I'd check the connector end at the radio really carefully. Mag mount pigtails are notoriously hit or miss from the factory and sometimes the center pin isnt making solid contact or the braid is barely hanging on inside the PL-259. I've seen brand new antennas right out of the box with garbage terminations.

Also try sliding the mag mount around to a few different spots on the roof — ground plane geometry can do weird things with the UHF readings especially on a truck with all the bodylines and curves. Dead center of the roof usually works best. If neither of those fixes it then yeah I'd just re-terminate or swap the pigtail with some better coax.

i had pretty much the exact same setup on my old ranger and the tram pigtail was the problem both times lol. just replaced it with a short run of LMR-240 and it cleaned right up on 70cm. the stock coax on those mag mounts is kinda trash tbh