so ive been running a mag mount diamond NR770H on my F250 for about two years now and it works fine, hits all the local repeaters no problem, but i keep reading that a properly mounted through-hole or lip mount antenna is noticeably better and i guess i never really stopped to think about why that would be.

the truck has a steel roof obviously so the ground plane shouldnt be the issue right? is it just the coax routing and the fact that the mag mount cable has to go through a door or window? because mine goes through the rear door seal and im pretty sure thats lossy but i honestly dont know how much it matters on 2m/70cm.

been thinking about doing a proper NMO mount on the roof but that means drilling and i kind of dont want to do that unless it actually makes a real measurable difference. anyone actually done a before/after on this kind of thing?

the coax routing through the door seal is definitely part of it but honestly the bigger thing is the ground plane contact. mag mounts are never quite as solid as a direct mount, theres always a tiny bit of inconsistency depending on where exactly the magnet sits and how clean the roof is. on a big truck roof you probably have a pretty decent ground plane so youre not losing a ton but its not the same as a bonded NMO mount.

i did exactly this swap on my tacoma maybe three years ago, went from a lip mount to drilling a proper NMO hole and running the coax internally through the headliner. honestly the SWR got a little better and i think reception improved slightly on weak signals but im not gonna sit here and tell you its night and day on local repeaters. if you mostly do local stuff the mag mount is probably fine. if you start doing any weak signal work or APRS where every dB matters then yeah the proper mount is worth it.

the coax through the door seal though, yeah get rid of that. even if you dont drill, running it through a grommet or finding a cleaner path makes a difference just in terms of not slowly destroying your coax jacket.

drilled two trucks and never regretted it. resale value argument never made sense to me, a small NMO hole with a cap in it is not gonna tank the value of a vehicle. the cleaner coax path alone is worth it imo, i used to get all kinds of weird noise running the cable through the door and once i went internal that mostly went away.