so ive been sitting on doing the mars/cap mod on my FT-857D for probably two years now, always felt a bit nervous about opening it up even though i know its literally just moving a diode. finally got around to it last weekend and honestly it went fine, took maybe 20 minutes including the time i spent second-guessing myself and reading the service manual three times.

the main reason i wanted it was just for some EMCOMM stuff where we occasionally need to go slightly outside the normal ham bands, nothing crazy. but while i had the thing open i also noticed the fan mod people talk about where you jumper the fan to run at lower speed constantly instead of kicking on hard when it gets hot. did that too. the fan noise on these radios always bugged me during rag chews, the sudden blast of air is pretty distracting.

anyway my question is whether anyone has done the internal ATU mod or added an aftermarket one to these, i know the 857 doesnt come with a built in tuner and ive been running an LDG externally forever but its kind of a pain in the field. wondering if theres a cleaner solution that others have figured out.

yeah the MARS mod on those is dead simple, Yaesu basically made it trivial on purpose i think. glad it went well.

on the ATU question -- ive seen a few people mount an LDG YT-100 basically velcro'd to the bottom of the 857 and use the CAT cable to get semi-auto tuning, its not truly internal but in the field it acts like one unit. not elegant but functional. the real internal solution would be swapping to an 897D which had the tuner option but obviously thats a whole different radio. there was a guy on one of the yahoo groups years ago who actually stuffed a miniature tuner board inside the 857 chassis but i never saw a complete writeup and i suspect it was more trouble than it was worth thermally.

the fan mod is worth it just for sanity reasons alone, agree with you there. mine would kick on and scare me every time during a quiet net.

i did the tx mod on mine too but i bricked the display doing something unrelated lol so take that as a cautionary tale about messing around inside while youre already in there. dont get overconfident and start poking at connectors that have nothing to do with what youre trying to do

no idea on the ATU thing sorry, i just run a manual tuner and deal with it