so i've been running a FT-7900R in my truck for about 3 weeks now and the install was kind of a mess at first — i had the power leads running too close to the ignition wires and was getting all kinds of garbage. finally rerouted everything direct to the battery with a fuse holder close to the battery like everyone says to do and that helped a ton. antenna is a Tram 1185 on a mag mount on the roof, coax goes through the door jamb.

but now im getting this kind of pulsing noise on receive, sort of rhythmic, speeds up when i rev the engine. i think its alternator whine? ive read about those little ferrite filters and also something about a ground loop but honestly im not 100% sure what the actual fix is here. radio works fine, i can hit the local repeater no problem, its just annoying. anyone dealt with this before or know what to actually try first before i start buying random stuff

yeah that's almost definitely alternator whine. the rpm-dependent noise is the giveaway. few things to check — first make sure your radio chassis has a solid short ground directly to the vehicle body, like a bolt on the firewall or somewhere close, not just relying on the power cable ground. sometimes people run a long ground wire back to the battery thinking thats better but it can actually pick up more noise.

if your grounding is solid and its still there, a ferrite choke on the power leads close to the radio can help, or sometimes one on the coax feedline right at the radio. I've also seen a small inline noise filter on the power line do the trick. they're only a few bucks. but ground the radio properly first before anything else, thats usually the culprit in my experience.

had the exact same thing in my old jeep with a 7900, drove me crazy for months lol. for me it ended up being the mag mount coax itself — the shield wasn't making great contact with the mount and it was picking up all kinds of crud. i swapped to a NMO mount through the roof and the noise basically disappeared. mag mounts are convenient but they're not always the greatest for RF grounding especially on vehicles with weird roof coatings. just something to consider if the power line stuff doesn't sort it out