so i picked up a Yaesu FTM-400 a few months back and it's been sitting in the box because i kept putting off the install. finally got around to doing it this past weekend and overall it went pretty well but i have a couple things bugging me.

first the antenna situation — i went with a Tram 1185 on a lip mount on the trunk lid of my F-150. seems to work okay on 2m but im not totally confident in the ground plane since its a lip mount and not a through hole. should i be worried about that or is it good enough for mobile use? ive heard people say lip mounts are fine and ive heard people say they're terrible so hard to know who to believe.

second thing is the radio is mounted under the dash and the head unit is up on the dash on a RAM mount. ran the cable through the back and it all looks clean but i noticed the receive audio has kind of a low hiss even when squelched — like i can hear it if the truck is quiet. not sure if thats normal for this radio or if i have a ground loop or something. the power leads are going direct to the battery with an inline fuse which i thought was the right way to do it.

been licensed about two years, mostly HF at home but wanted to get into the local repeaters while commuting. any advice from folks who've done this kind of install appreciated.

lip mounts get a bad rap but honestly for VHF/UHF they work fine in most cases. you're not trying to work DX on 40m here, the wavelengths are short enough that a decent lip mount with good contact will get you on the local repeaters no problem. i ran one for years on my Tacoma before i finally drilled a hole and the difference was pretty minimal on 2m. the main thing is making sure the mount itself has solid metal-to-metal contact and isn't sitting on any paint or rubber gasket material.

the hiss thing — if its there with squelch closed that does sound a bit odd. first thing id check is whether it changes when you rev the engine or turn accessories on and off. alternator whine usually shows up as a pitch that changes with RPM, a ground loop can be more of a constant hum or hiss. try running a separate ground wire from the radio chassis to a good bare metal point on the truck body if you havent already, sometimes the chassis ground through the power leads isnt enough. the FTM-400 is a good radio, i dont think its the radio itself.

i did almost the exact same install about a year ago, different radio but same truck actually (also an F-150). the hiss drove me crazy for a while and it turned out to be the USB port i had plugged in for my phone charger of all things. unplugged that and most of it went away. might not be your issue but worth trying process of elimination with stuff like that before you start chasing ground loops.

also the RAM mount setup for the head is the way to go imo, so much easier than trying to find a spot to permanently mount it and you can pull the whole thing off if you leave the truck somewhere sketchy.