so anyway i finally got the dual band mobile working the way i want it after like three weeks of messing around and figured id share what tripped me up in case it helps anyone else going through the same thing

i went with a Yaesu FTM-400 and mounted it in a RAM mount setup under the dash. the head unit is on a little arm where i can see it without looking away from the road too much. first problem i ran into was the coax routing — i tried running it under the door sill trim and picked up a ton of ignition noise from somewhere, clicking in time with the RPMs. drove me nuts for a week. eventually i rereouted the coax along the center tunnel instead and grounded the radio directly to the chassis with a short heavy strap and that pretty much killed the noise floor issue completely.

the antenna is a Diamond NR770HB on a lip mount on the trunk. not the most ideal location but i rent so i didnt want to drill. SWR came out around 1.4 on 2m and about 1.6 on 70cm which im okay with for now. hitting the local repeaters on 2m without any trouble and even worked a few stations simplex on the highway which was fun.

if anyone is still fighting ignition noise i really cant stress enough how much a proper chassis ground helps, like it made a night and day difference for me. the factory ground points are usually garbage for rf purposes

yeah the ignition noise thing is so common and it drives people crazy before they figure out whats going on. good call on the chassis ground, thats almost always the culprit. i had similar issues in my old truck with a TM-V71A and it turned out one of my ground straps was corroded under the lug and i didnt notice it for months. looked fine visually but had like 2 ohms of resistance across it which is terrible for rf ground.

the lip mount antenna placement will work fine honestly, i ran a similar setup for years. if you ever want to squeeze a little more out of it on uhf you might try repositioning it slightly more toward the center of the trunk lid if thats possible with your mount — gets you a bit more ground plane symmetry. but really at 1.6 swr youre not losing much at all, most of the power is still getting out.

nice choice on the FTM-400 too, the APRS integration on that radio is really handy for mobile use once you get it configured. took me a bit to get the smart beaconing dialed in but once it was set it just works.

this is really helpful, im about to do my first mobile install in the next few weeks and the noise issue is exactly what im worried about. quick question — does the type of car matter much for how bad the noise gets? i have a newer car with a lot of electronics and i keep reading that modern vehicles are worse for this kind of thing