So after like three weeks of messing around with cable routing and trying to figure out where to actually mount the head unit I think I finally have a decent setup going in my F-150. Running a Yaesu FT-7900 which I picked up used off a local ham at the club meeting last month. Good radio so far, no complaints.

The antenna is a Tram 1185 dual band mag mount sitting on the roof right now but I want to go permanent at some point. My main thing is the coax run — I ended up going through the firewall with a rubber grommet I found at the hardware store and it seems okay but honestly I'm a little paranoid about it rubbing through over time. Anyone else done this and had issues? Or am I overthinking it.

Also kind of a separate thing but the radio sits in my center console area and when I key up on 70cm especially I get a weird low hum through the truck speakers. Not terrible but its annoying. I think its a ground loop maybe? I dont really know how to diagnose that properly. Any tips would be appreciated, been lurking here for a while and you all seem to know your stuff.

The coax through the firewall thing is pretty common and honestly your instinct to protect it is the right one. What I usually do is find an existing factory grommet that already has wires going through it and carefully work the coax alongside those — most vehicles have at least one spot like that. If you punched your own hole just make sure whatever grommet you used fully covers the metal edge all the way around. Split loom over the coax on both sides of the firewall doesnt hurt either, cheap insurance.

For the hum on the speakers, yeah thats almost certainly a ground loop. The usual fix is to make sure your radio is grounded directly to the chassis with a short heavy wire rather than relying on the power cable ground return. Some people also use a ground loop isolator inline on the audio but I'd try proper grounding first before adding anything. If the radio's power is coming from a long run back to the battery that can contribute too. What gauge wire did you use for power?

oh man I had the exact same hum problem when I put my 5100 in my Tacoma last year. drove me crazy for like two weeks. turned out the issue for me was my power wire was running right next to the audio harness for a stretch inside the dash. rerouted it away from those and it went away almost completely. might be worth checking if thats the case for you too before you go buying anything