so i spent most of saturday getting the FTM-500DR installed in my truck and overall i'm pretty happy with how it came out. ran the power leads directly to the battery like you're supposed to, used 10 gauge wire with an inline fuse close to the battery, and the radio itself is sitting in a RAM mount on the dash. antenna is a Diamond NR770H on a mag mount on the roof for now until i figure out where i want to drill.

the problem is when i key up i get this buzzing noise through the audio. it's kind of hard to describe but it almost sounds like it pulses with engine RPM? it doesn't do it when the truck is off, only when running. already tried moving the coax away from the power leads but that didn't really help. signal reports from the local repeater guys have been decent so it seems like it's only affecting what i'm hearing on my end, not what i'm putting out, but it's still annoying as heck.

anyone dealt with this before? i'm wondering if it's an alternator thing or maybe a grounding issue. i'm not super experienced with mobile installs so i might have done something dumb without realizing it.

that sounds like classic alternator whine, pretty common with new installs. the RPM pulse thing is the giveaway. a few things to check — first make sure your power ground is going to the same point as the chassis ground for your radio if you're running a separate chassis ground at all. sometimes people run the negative lead to a body bolt somewhere instead of back to the battery and that can cause all kinds of noise issues.

if that doesn't sort it out, try a ferrite choke on the power leads close to the radio. i had almost the exact same issue on an old IC-2300H install years ago and a snap-on ferrite on the positive lead killed most of it. you might also want to check how your coax is routed — even if it's not touching the power wire, running it parallel for any length of run can pick stuff up through inductive coupling. try routing the coax on the opposite side of the vehicle from the power leads if you can manage it.

mag mount is also worth looking at, the grounding contact on those can be iffy sometimes and a poor antenna ground can make the radio noisier than it needs to be.

yeah i had something similar when i put a radio in my jeep, drove me nuts for like two weeks. turned out my fuse was way too far from the battery. i thought i had it close but it was actually closer to the firewall. not saying thats your problem but worth double checking everything.

also the FTM-500 has some squelch and noise blanker settings in the menu that might help in the meantime while you track it down. i dont remember the exact menu path off the top of my head but its in there somewhere.