so i've been running my FT-7900 in the house for about a year just on a desk with a temporary mag mount on the window and decided to finally do a proper mobile install in my F-150. ran the power cable directly to the battery with a fuse near the battery, which i know is the right way to do it. antenna is a diamond NR770HNMO on a lip mount on the trunk lid — well i mean the tailgate i guess since its a truck.

the problem is when i key up on 2m everything sounds fine to me but people are telling me they hear a buzzing or whining noise in my audio that kind of changes with engine RPM. i've heard of alternator whine before but i thought running direct to battery would mostly fix that. the coax shield is grounded at the mount but im wondering if maybe the lip mount isnt making great contact with the truck body. or could it be the audio cable from the radio? i ran everything pretty close together which maybe was dumb.

anyone dealt with this before? kinda at a loss here

yeah alternator whine is super common and going direct to battery doesnt always fix it by itself. the noise usually gets into the radio through the power leads not through the antenna side. first thing i'd try is a ferrite choke on the power cable right at the radio, just snap a couple of the big clamp-on ferrites on there and see if that changes anything. also check your ground — sometimes people run the negative lead back to the chassis instead of all the way to the battery negative and that can introduce noise into the path.

the lip mount grounding is worth checking too honestly. i had a similar setup years ago and the lip mount was just barely making contact, cleaned it up with some sandpaper where it touched the metal and it made a big difference. doesnt hurt to run a short jumper from the mount to a good chassis ground point just to be sure.

might also be worth trying a ground loop isolator on the audio line if you have anything connected there like an external speaker or phone. i had whine on my mobile setup for like 3 months before i figured out it was actually coming through the USB cable i had plugged into my phone which was plugged into the car charger. sometimes the noise path is not obvious at all lol