so ive been sitting on this for a while but last saturday i finally pulled the trigger and did the mars/cap mod on my FT-857D to open up the TX range. not planning to transmit outside the ham bands obviously but i wanted the flexibility for some EMCOMM stuff where we might need to hit certain MURS or business freqs in an actual emergency and our EC has been pushing everyone to do it.

anyway the mod itself wasnt bad, just the one diode removal on the main board if i remember right, took me maybe 45 minutes including the time i spent second guessing myself with the iron. but now im down a rabbit hole because someone in my local club mentioned theres also an internal mic gain mod that can help with the 857's somewhat mediocre audio on SSB and i cant find a consistent writeup on it. some guys say adjust R1015 or whatever it is, others say just get an external mic preamp and call it a day.

also thinking about doing the fan mod at some point, the thing runs warm and the fan curve seems pretty conservative from the factory. has anyone actually measured temps before and after on that one or is it one of those mods where you just feel better but nothing actually changes

the fan mod is real, i did it on mine maybe two years ago. swapped to a higher cfm 60mm fan and wired it to come on a bit sooner, not a huge difference at QRP levels obviously but if you're running it near full power for any length of time on digital modes the heatsink temp is noticeably lower. i used a cheap IR thermometer to spot check it before and after and was seeing maybe 8-10 degrees C less at the heatsink after 10 minutes of FT8 at 50W. whether thats worth the hassle is up to you but i figure the finals will thank me eventually.

on the mic gain thing — i just use an external preamp, specifically a little cheap Behringer unit i had lying around. honestly the audio reports got way better and i didnt have to touch anything inside the rig. the internal pot adjustment is fiddly and easy to overdo, i watched a guy on a zoom call with our club accidentally introduce a hum by messing with the grounding when he had the thing open for that. not saying dont do it just saying the external route is lower risk.

yeah the mars cap mod is pretty standard stuff, i did mine years ago on a 897D which is basically the same guts. the diode thing takes like two seconds once you actually find the right spot on the board, the hard part is just not getting nervous and slipping with the iron near other components.

one thing i'll throw out there — if you're doing emcomm work and want to actually be useful on non-ham freqs, make sure you understand what your region's ARES/RACES protocols actually say about it because in some areas they're pretty strict about documented authorization even in a declared emergency. your EC should know but ive seen some confusion on this at exercises. anyway not trying to be the fun police just something to keep in mind before you start calling on 151 MHz at a drill and somebody asks questions