so ive been working on getting my FT-857D installed in my F-150 for about three weekends now and i finally got everything bolted down and ran the power cables direct to the battery with an inline fuse, which everyone says to do and yeah it makes sense. the radio works great on HF but on 2m and 70cm im getting this annoying whine in the audio that changes pitch with the engine RPM. like when i rev it up the noise goes up too, classic alternator whine i think? but ive also got some kind of buzz that doesnt change with RPM and im not totally sure what thats from.

antenna is a Diamond NR770HB on a mag mount right now, sitting on the roof. the coax is just routed through the door seal temporarily. im using RG-8X for the run which is maybe like 8 feet total. the power leads are about 5 feet on each side and i havent done any ferrite chokes yet because i wasnt sure if that was actually necessary or kind of overkill.

has anyone dealt with this? wondering if i should start with ferrites on the power leads or if the coax routing through the door is actually causing some of the issue. also not sure if a mag mount is even a great ground plane on a modern truck with the plastic bed cover situation im dealing with

yeah that RPM-varying whine is almost certainly alternator noise getting into either the power leads or the coax shield. the first thing id do honestly is add a ferrite choke right at the radio on the power leads, like snap-on types work fine for this, nothing fancy. also check that your power cable isnt running parallel to any factory wiring for long runs because that can couple noise in too.

the door seal coax routing is probably contributing at least a little since youre not getting a great shield connection at the entry point. if you can get the coax in through the firewall thats almost always cleaner. for the mag mount ground plane issue on trucks with plastic stuff yeah its real, the NR770HB will work but youre not getting ideal performance. a lip mount or a hole mount through the roof would be a big improvement but i get that its a bigger commitment. start with the ferrites and see how much that cleans things up first before you go drilling holes anywhere

I had almost the exact same thing happen when I put a Kenwood TM-V71A in my Tacoma a few years back. Drove me absolutely crazy for like a month. Turned out in my case the main culprit was the coax shield not being bonded to the vehicle chassis properly — the mag mount was sitting on a spot that had some kind of paint or coating underneath and wasnt making great contact. wiped it down with some isopropyl and suddenly like 80% of the noise just went away. worth checking before you go adding a bunch of chokes everywhere. also the constant buzz that doesnt track the RPM, in my truck that ended up being the LCD backlight on the radio itself getting picked up, which sounds weird but apparently its a thing with some installs.