so ive been running a mag mount on the roof of my F150 for about two years now and finally decided to do a proper NMO through the cab roof but then my buddy tells me i should put it on the bed rail instead because drilling the cab is permanent and resale value blah blah blah. i get that but now im second guessing the whole thing because i remember reading somewhere that mounting behind the cab creates a pretty significant shadow on the forward lobe especially on UHF and i drive mostly on the highway heading north so basically all my repeater hits are ahead of me.

anyone actually done back to back testing on this? like cab roof vs bed mount on a pickup? or even just have a feel for how bad the shadowing is in practice. im not trying to win a contest here just want reliable repeater access on 70cm while driving. running a 5/8 wave whip for 440 if that matters.

the shadowing is real but honestly for just hitting repeaters it probably wont kill you. i ran a lip mount on the bed of my tacoma for a few years and yeah there were spots where i'd lose a repeater just as i crested a hill heading into it but i always figured that was terrain not the antenna position. moved the antenna to the cab roof eventually and it did seem a little more consistent but im not sure i could say definitively it was the mount location vs just normal path variation.

if you're going NMO and committing anyway i'd just do the cab roof. resale argument is kind of weak, a clean NMO hole with the right grommet is barely noticeable and you can plug it if you ever sell. the bed rail thing always seemed like a compromise to me, you get a worse ground plane AND the shadow issue.

cab roof, no question. the ground plane on a bed mount is also sketchy depending on how your bed is constructed, some of those composite beds are basically worthless for RF. on 70cm you really want a solid continuous ground and the cab roof gives you that. the shadow off the back window and cab structure at 440 mhz is noticeable in my experience, probably 3-6dB in the worst case direction which on a marginal path to a repeater thats the difference between quieting the squelch and not.