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(Long post, sorry. Synopsis/TLDR at the end) Does impedance or cable length matter on a chassis ground for a mobile setup? I’ve read several posts and a couple articles about proper chassis grounding of the antenna (specifically the ground plane, and yes I know they are different) but can’t seem to nail this one detail down. Some sources say use an exposed grounding strap less than 10” long, others refer to grounding NEAR or TO the battery ground on the vehicle body (not the battery itself). I assume they are not using exposed braid for the multiple feet between their antenna and engine bay, (I could be wrong,) so potentially coax cable? But no mention of what kind. The only thing consistently stated (which makes sense) is to make sure both ends of the grounding cable actually contact bare metal. In my mind (not an electrician and new to radios) it would make sense for the ground to have less resistance than the input as it is the “escape route” for unused energy, preventing it from feeding back down the outer braid of the coax. On the other hand it also makes sense (in my head) for the ground to match the input resistance so it doesn’t allow energy to escape that should be turned into radio waves. Again, not an electrician, new to radios so I’m probably not thinking of this the right way! In case it’s useful, here’s what I’m working with conceptually at the moment as far as radio/antenna setup: I have a MXT575 and am waiting on a Larsen LP450NMO antenna to show up. I’ll be mounting it on a custom ground plane mount (24”x24” aluminum plate) behind the rear roll bar of my Jeep JKU with a hard top, high enough to clear the roll cage. The radio will be mounted directly under it, maybe 12”-16” of coax between the two. Before anyone asks, I am trying to avoid external mounting of the antenna as a personal preference. Also, short of drilling holes in my top this gets the antenna above the roll cage which is a plus! Synopsis/TLDR: 1: does cable length and/or type (shield vs unshielded) and/or resistance matter when chassis grounding a mobile antenna ground plane? 2: does grounding location matter? Thanks in advance for any info everyone!

Is there a simple, plug-and-play way to boost the power going to the antenna in terms of wattage? Perhaps something in the coax line running to the antenna such as a signal amplifier?

So I have had some people swear up and down that LMR-400 should not be used on a repeater. That after some time the sensitivity will degrade and it "will cause noise". Now for what I use mine for, it is probably good enough. But I have researched a little bit, and found that yes, for repeaters that experience heavy use this could eventually become an issue. However, it seems that is the case for regular LMR-400. I have found that this noise is actually from wire braid coax, and that you can actually buy LMR-400 that isolates the the two shields so the wire braid is not touching the foil, and does not cause the noise. My question is, is this a serious enough problem for the average repeater owner to even care? My opinion is no.

So a few weeks ago I took my repeater offline due to transmitter issues. I run a RKR1225 (rack mount version of the GR1225) and of course this repeater is known for its issues with burned out finals in the PA. At the time the unit was putting out .1W of its 25W of power. I didn't have time to pull the unit from the rack and disassemble the shelf so for a bit, out of wanting to protect components, I just shut the repeater off. Fearing a PA failure I was in no rush to dismantle anything until I knew I could get the parts or ship it out to a shop for repairs. When the time came earlier this week, I contacted a shop who said I needed to confirm the PA had not already been replaced as they couldn't repair an already repaired amp. So I pulled the shelf from the rack and began to dismantle it so I could remove the radio body, however when I removed the TX jumper from the radio, I found that the coax had failed, separating from the connector. From just looking at it you couldn't tell, but everything, the center pin and the shield, had come apart and simply slid out of the end of the connector and rest in my hand!! Concerned the PA may have been damaged because of this, I found a crap jumper I had set aside when I was given the double shielded jumper. I ran it through the meter and into a dummy load and behold, TX power returned to 25W! A little more testing, including the duplexer showed everything was working fine. I figured I would test the coax separately with a test meter for coax and sure enough it showed high resistance and feedback in the little 1' jumper. In the end I purchased 2 jumpers, a bit longer than the one I was replacing as I believe the older one could have been pulled on during install. I replaced both the RX and TX jumpers with LMR240 coax and the result is that not only did the TX power come back, but the range extended a little bit as well. This is just a reminder that even the simplest of things such as a jumper can mimic larger more costly problems. I believed it was going to be nearly $150 to repair the repeater and I even considered just replacing the unit with one that could run 50W on a 100% duty cycle. All I really needed was a $15 jumper to replace the one that failed. For those of us diagnosing issues for repairs we need to keep in mind that its not always the common problem causing the issue, and we need to make sure we always check the simple stuff we often overlook such as jumpers which are not a common failure point.