so i've been running a little handheld velcroed to the dash for like two years now which i know is embarrassing but i finally pulled the trigger on a proper mobile setup. picked up a used FT-7900R and spent last saturday running coax and doing the power wiring the right way, straight to the battery with an inline fuse and everything.

the antenna situation is where im not totally sure i did it right though. i've got a NMO mount drilled through the roof which was terrifying by the way, but the coax run i did goes kind of under the headliner then down the a-pillar and under the carpet to the radio under the seat. total run is maybe 12-13 feet. i used some RG-58 i had laying around because i figured the run was short enough it wouldnt matter much. is that actually okay or should i swap it for LMR-400 or at least RG-8X? i dont wanna redo the whole thing but i'll do it if i really should.

also when i key up on 2m the SWR reading on the radio itself shows like 1.3 which seems fine but on 70cm it jumps to around 2.1. antenna is a Tram 1185 dual band. is that normal for that antenna or did i maybe not get the NMO connection tight enough?

RG-58 over a 12 foot run is honestly fine for VHF/UHF, you'll lose maybe half a dB compared to LMR-400 over that distance and you'd never notice it in real world use. don't tear it apart just for that.

the SWR on 70cm is worth looking at though. the Tram 1185 is a decent antenna but ive seen some of them come a little off on 70cm out of the box. first thing id check is just making sure that NMO connector is threaded down all the way and there's no coax braid sneaking into the center pin area. those mobile NMO connections can be finicky when you first put them together. if the connection checks out and it's still 2.1 i honestly wouldnt lose too much sleep over it, 2.1 on UHF mobile still works fine for most local repeater work. your radio isnt gonna melt or anything.

oh man i remember drilling that first hole in my roof, i stood there with the drill for probably 20 minutes before i actually did it lol. looks so much better than a mag mount though once its done.

i have the same antenna actually and mine reads about 1.8 on 440 which i was also a little worried about but its been working totally fine for like a year and a half hitting repeaters all over the place so i think its just kinda how that antenna is. maybe someone who knows more can say for sure but im not stressing it