so ive been running a mag mount on the roof of my truck for about two years now with a diamond SG7900A and honestly its been fine but i keep reading that a proper NMO through-the-roof mount is the way to go for a permanent install. the mag mount does slide around occasionally when i hit highway speeds and ive got this weird patch of paint rubbing off under it which is annoying.

the thing holding me back is obviously drilling a hole in my truck roof. feels like a commitment. currently running an IC-2730 in the cab and i mostly do local repeater stuff plus some simplex when i go camping with buddies. nothing serious like contesting or anything. is the NMO actually that much better electrically or is it more just about the mechanical stability? i can never find a straight answer on this that isnt someone trying to sell me something

done both and honestly the NMO is just better in every way except for the part where you drill a hole. mag mounts always have that lossy contact between the magnet and the roof acting as part of the ground plane, and depending on your vehicle you might only be getting like 50-60% of the groundplane you think you are. NMO sits flush, makes solid contact, proper ground, done. the antenna itself performs noticeably better especially on 70cm where that contact resistance really starts to matter.

for what its worth i used a Larsen NMO mount on my last truck and ran it for 6 years with zero issues, no water intrusion, nothing. just use a good self-amalgamating tape wrap and seal the inside too. the commitment thing i get but once you do it youll wonder why you waited. also the SG7900A is a good antenna, should do real well on a proper mount.

yeah the sliding is the thing that finally made me do it too. woke up one morning and my mag mount had blown completely off on the interstate, antenna and coax just gone. luckily didnt cause an accident but man that was a wake up call. drilled the hole that weekend. if youre keeping the truck more than another year or two just do it, resale value hit is basically nothing