so ive been sitting on doing the mars/cap mod on my ft-857d for probably two years now, kept putting it off because i was worried about voiding warranty which is kind of a joke since the thing is like 8 years old at this point. anyway finally cracked it open last weekend, it's literally just moving one jumper on the main board, took maybe 20 minutes including the time i spent double checking the diagram because i was paranoid.

but thats not actually the main thing i wanted to talk about. while i had it open i went ahead and did the collins filter mod too, swapped in a 500hz CW filter in the IF and the difference on 40m at night is pretty substantial. crowded band conditions are just way more manageable now, i can actually pull out signals that were getting buried before. the filter itself was like 45 bucks from universal radio i think, installation wasnt bad if you're comfortable with a fine tip soldering iron.

anyone else done any mods to theirs? curious if the audio filtering mods are worth it, ive seen some stuff about modifying the TX audio chain for better voice quality on SSB but i cant find a good writeup that isnt from 2009 and half the links are dead.

yeah the collins filter makes a real difference, did that on mine probably 4 years ago. the 500hz is nice but i actually went with a 300hz because i do a lot of qrp cw stuff and i wanted it as tight as possible. some guys say 300 is too narrow but honestly once you're used to it you don't want to go back.

for the TX audio thing you're talking about, there was a mod floating around involving changing a capacitor in the mic preamp section that supposedly opens up the high end a bit and gets rid of some of the boxy sound the 857 has stock. i want to say it was on eham or maybe the qrz forums but yeah finding it now is a pain. if you poke around k0bg's site he might have something or at least a link that still works. the stock TX audio on that radio is honestly pretty mediocre for SSB, so anything that helps is worth trying IMO.

i did the MARS mod on mine and thats about as far as ive gone, a little nervous about getting into the IF section tbh. did you use the Yaesu service manual for the filter install or find a different writeup? i've seen a couple versions floating around and wasnt sure which one was accurate for the later production runs of the 857d since apparently they changed the board revision at some point.