so ive been putting this off for like 6 months but i finally got the FT-857D mounted in my F-150 last weekend. runs on VHF and UHF just fine so far, been hitting the local 2m repeater with no problem. i ran the power leads directly to the battery with an inline fuse which i was told is the right way to do it.

my main question is about the antenna. right now im using a mag mount i had sitting around, its a dual band whip and its just sitting on the roof. works okay but i get some noise when the engine is running, not terrible but noticeable. i was wondering if a proper NMO mount would make a difference or if its more likely something else causing the interference. also the mag mount keeps sliding a tiny bit when i make turns which is kind of annoying.

second question is kind of dumb but how are you guys routing your coax inside the cab? i ran mine through the door jamb which seems fine but i feel like im pinching the coax a little. is that a real concern or am i overthinking it

the noise when the engine is running is almost certainly alternator whine getting into the coax through the mag mount. mag mounts don't always make a great ground connection especially if there's any paint or coating under them, even a thin factory clear coat can mess with the RF ground. an NMO mount drilled through the roof with a proper ground to the body of the truck will make a huge difference. its the right way to do it long term anyway.

on the coax through the door jamb thing -- yeah i'd be a little careful with that. over time the flexing when you open and close the door can work the center conductor loose or crack the dielectric. most people i know either go through a grommet in the firewall or use one of those flat coax pieces that are made to run under a door seal. takes a bit more work but its worth not having a intermittent connection six months from now when you cant figure out why your SWR is suddenly bad.

congrats on getting it done, the 857 is a great little radio for mobile. i had one in my jeep for a couple years. re the sliding mag mount -- if the roof curves at all or theres a lip near where you put it, that'll cause it to drift. some people put a thin rubber mat under the magnet to help it grip better but honestly for a permanent install just do the NMO, youll thank yourself later.

the coax pinch is a real thing btw, dont ignore that