so ive been running a mag mount diamond on my F-150 for about two years now, mainly for 2m/70cm and it works fine i guess but ive always had this nagging feeling im leaving performance on the table. the mount sits on the roof and the cable runs down through the door jamb which i know isnt ideal and i do get a little bit of noise from the engine on certain rpms which might be a grounding thing or might be the coax situation, hard to say.

anyway my buddy who does a lot of APRS and linked repeater work says just drill the roof and put in a proper NMO mount and be done with it. he's probably right but i keep putting it off because, well, drilling a hole in a 4 year old truck feels permanent. has anyone done this and actually noticed a meaningful difference on receive or is it mostly just the cleaner install that makes it feel better? also wondering if a longer antenna like a 5/8 vs the 1/4 wave i have now would help on the repeaters that are a bit further out.

drilled my 4Runner about 8 years ago and never looked back. the difference in receive on weak signals is noticeable, not huge but real, mostly because you finally have a solid ground plane doing what its supposed to do instead of relying on magnetic coupling through paint. the noise issue you mentioned almost certainly goes away with a proper NMO because the cable isnt flexing around a door seal anymore picking up ignition garbage.

if youre going 5/8 wave on 2m just make sure you account for the gain pattern because the takeoff angle is lower and that actually works against you in some hilly terrain where the repeaters are up high. for flat areas and highway driving its great. i use a larsen NMO150/450 and its been on the truck through heat and cold with zero issues, the connector is solid and water hasnt been a problem with the standard grommet kit.

yeah the engine noise on certain rpms is almost always the coax routing, i had the exact same thing with a door jamb setup on my old chevy. once i rerouted it properly and used a ferrite bead near the radio end it was basically gone. that said i still havent drilled my current car so im not one to talk lol