so i've had my FT-857D for probably 6 years now and i always kind of knew about the mars/cap mod to open up the TX range but never bothered because honestly i mostly just work HF and the occasional VHF simplex. but i picked up a second one cheap at a hamfest last month and figured id try the mod on that one first before touching my main rig.

the mod itself is dead simple, just a couple of diodes on the main board, theres a dozen writeups online and they all basically say the same thing. took me maybe 20 minutes including the time i spent second-guessing myself and staring at the board with a flashlight. after that the rig transmits way outside the ham bands which i obviously dont plan to use, but the more useful thing for me was that the RX opened up too and i can now monitor some stuff i couldnt before without a separate scanner.

anyway the second thing i did was the internal fan mod because that stock fan is genuinely annoying when youre doing any kind of extended operation. swapped it out for a quieter 12v fan and did a simple resistor mod to slow it down a bit at lower temps. havent had any heat issues and its so much quieter now. just curious if anyone else has done other mods to theirs, ive seen some stuff about the CAT interface and maybe improving the stock mic preamp but havent dug into those yet.

the fan mod is worth it on its own, i did that about a year into owning mine and honestly the stock fan sounds like a cheap box fan on high. i used a noctua 40mm, had to adapt the connector but its basically silent now. if you're thinking about the mic preamp thing, theres a mod floating around that adds a small electret bias circuit and it does make a noticeable difference if you use the internal mic connector a lot. i run an SM-50 so i never bothered but a buddy of mine did it for his shack mic setup and said it cleaned up some of the low end.

one thing i'd also look at is the AGC mod, there's a cap swap that gives you a bit more control over AGC behavior on crowded bands. not a huge deal but on 40m during a contest it can help. i forget which cap it is off the top of my head but its in the N4PY writeup i think, or maybe the k0bg page. one of those.

yeah the rx coverage opening up was the main reason i did it on mine tbh, i use it as kind of a shack receiver when im not actually transmitting. did you do anything to the squelch sensitivity while you were in there? i feel like the VHF squelch on mine has always been a little finicky and im not sure if thats a known thing or just my unit.