so i've been running my FT-7900R in the truck for about three months now, had it just kind of sitting on the seat with a mag mount which i know is terrible but i finally got around to doing a proper install last weekend. ran the power leads direct to the battery with an inline fuse, used the existing grommet in the firewall to route the cable, mounted the radio under the dash on a RAM mount bracket thing.

problem is ever since i did the proper install im getting this weird buzzing noise on receive that kind of pulses with the engine rpm. didnt have it before with the janky mag mount setup which makes no sense to me. transmit seems fine, people say i sound good. its just annoying as heck on receive especially on 2m simplex where there's not a lot of signal to cover it up.

anybody dealt with this before? i'm wondering if its the alternator but i dont really know how to chase that down. the power leads are pretty close to the engine harness where they go through the firewall, maybe thats it?

classic alternator whine, yeah. the rpm-following behavior is the giveaway. few things to try — first check that your radio chassis is actually grounded to the vehicle body and not just floating. sometimes the RAM mount isolates things a bit. short heavy gauge wire from the radio body to a good chassis ground point nearby can make a big difference.

also those ferrite cores / chokes can help a lot on the power leads if grounding doesnt fix it. snap-on type, put one close to the radio end. i had a similar situation in my old Tacoma and it turned out the ground strap between the engine block and chassis was corroded. tightened that up and most of the noise went away on its own. the routing close to the engine harness probably isnt helping either but i'd start with grounding before you start moving wires around.

yeah this happened to me too when i upgraded from a mag mount to a real install, felt backwards like it should have gotten better. ended up being my ground. i just grounded to a convenient bolt under the dash which turned out to be a terrible ground point apparently. moved it to a proper chassis screw and it was like night and day. dont overlook that.