i do have an update on the antenna, but it's not a "final" configuration yet! i got my hands on a Laird no-ground plane antenna and did some comparison testing. in my opinion, it's slightly better than the Midland - but not by very much. i'll explain...
the midland is sold as "pre-tuned to 462 mhz". the laird is ufh 450-470 - it's tuned to 450, and to better tune to 462 i should cut it a bit shorter. i've been afraid to do that - fearing that if i cut too much off, i could make things worse. right now my SWR is exactly 1:1 - i'm assuming because the anteanna is slightly longer than ideal for this frequency. but before cuting / tuning, i wanted to test it as-is.
so i road tested the laird and compared to the midland. the first thing i noticed was the laird no-ground plane definitely had more "reach" than the midland, by a few blocks. maybe about half a mile to a mile farther. so i drove in and out of where i thought the range would end, and noted on a map where coverage was good, bad (meaning no receieve either direction), or staticy (receive but with static).
where the range ended wasn't a hard cut-off. i found spotty areas just a bit father away that worked pretty decent. but overall, i was happy with the no-ground plane antenna being that it might have little better "reach" plus the spotty areas.
i then retested with the midland anteanna, driving the same route. this time the midland performed better than my test a few weeks ago, and i also noticed more spotty areas where i had signal but didn't expect to. so the midland was better this time than last time, but still not as good as the no-ground plane. i think the different results with the midland were just more thorough testing and different topography / weather.
in my test results, there were some spots that the laird worked and the midland didn't, and others that the midland worked and the laird didn't... but overall it seemed the laird worked better. i probably need a few more days to know for sure... but i guess that indicates there's not a huge difference.
the mxt275 also came with a mag-mount antenna. i road-tested that one also, having it sit on the very top of my tire carrier (where i'm thinking to move my mount to). it performed better than i expected. within a mile it sounded crystal clear, but after about 1 - 1.25 miles it cut out pretty hard. really makes me wonder how a 1/4 wave would perform mounted at that point - one day i will try that, but might take a few weeks for me to find all the parts i need and to make sure i have enough coax.
i found something else interesting with the two midland (mxt275 versus handheld gxt1000).
if i configure a PL tone on a channel (which is applied to tx and rx) and run channel-scan, it stops at a channel that has signal, and operates as carrier squelch. if i change to that channel manually, with PL set, I don't hear anything. but as soon as i scan, it'll stop and that channel and i hear the transmission. i was surprised at this - and tested it again using my handheld with no PL configured. the mobile 275 stopped and i could hear it (only in scan, not when just sitting on that channel).
i did the same test using the handheld as the receiver, with a PL set on the handheld, using the mobile to transmit with no PL. when the handheld is in scan mode and i transmit with no tone, the handheld stops at that channel, but i still hear no audio. so it more "pauses" the scan until there's no signal, then it moves on.
i just thought that was odd, especially on the mobile.... but admittedly, i probably should check the manual, but it was more fun to just try it.