So i've been putting off doing a proper mobile install for probably two years now and last weekend i finally pulled the trigger and got the FT-857D mounted under the passenger seat with a RAM mount for the control head on the dash. Looks pretty clean honestly, ran the power leads direct to the battery with an inline fuse, used about 10 feet of 10 gauge wire which i think should be fine for the power levels i'm running.

Problem is now i'm getting this whine on receive that goes up and down with the engine RPM. Classic alternator whine i guess? I tried wrapping the power leads around a ferrite core i had laying around and it didn't really do much. The antenna is a Comet CA-2x4SR on a lip mount on the trunk lid. Wondering if the issue is the antenna feedline running close to other stuff or if its a grounding thing. Havent really had time to dig into it further but it's pretty annoying on 2m especially.

Anyone dealt with this before? I know its a common problem just curious what actually worked for you.

Yeah alternator whine is super common and honestly kind of a rite of passage with mobile installs lol. First thing id check before anything else is your grounding. Like where is the radio chassis grounded? If you ran the negative all the way back to the battery but the radio body itself is just floating or connected to a chassis ground somewhere sketchy that can cause all kinds of noise. The rule of thumb a lot of guys use is short ground to chassis, short ground from chassis to battery negative, keeps the ground loop small.

The ferrite cores help sometimes but you really need the right mix for HF vs VHF noise. For alternator whine on VHF i've had better luck with a noise filter inline on the power leads, the Astatic or similar ones you can get for like 15-20 bucks. Also check if your antenna feedline is running parallel to any power wires for a long stretch, that can couple noise into the coax something fierce. Routing is huge. Good luck with it, it usually just takes some methodical troubleshooting.

i had the exact same thing with my 2720H in my jeep drove me nuts for months. Turned out the lip mount itself wasn't making great contact with the body and the feedline shield wasn't getting a clean ground path. Cleaned up the contact area and added a small grounding strap from the mount to the body and it cleaned up like 80% of the noise. Might be worth looking at that too, especially with a lip mount since they depend on that contact for the ground plane.