so ive been sitting on doing the mars/cap mod on my FT-857D for like two years now and finally just did it last weekend. not really for transmitting out of band or anything sketchy, mainly wanted it for some EMCOMM stuff where you occasionally need a bit of flexibility and also just to see what the radio could do.

the mod itself is pretty straightforward if you've cracked open a radio before, just a couple of diodes on the main board. took me maybe 45 minutes including the time i spent second-guessing myself and checking the diagram three times. radio came back up fine, alignment seems unchanged, and the extended TX is working as expected.

while i had it open i also went ahead and replaced the final fan with a quieter 12v unit i had laying around from a computer build. the stock fan on these is honestly annoying and the new one moves about the same air at lower RPM so thermals haven't been an issue.

anyone else done anything interesting to their 857 or similar rigs? im curious about the DSP filter mods people talk about, not sure if the aftermarket filters are actually worth it or if its one of those things that sounds good on paper

the fan swap is the first thing i did on mine too, shouldve been stock honestly. i used a Noctua NF-A4 which is overkill but dead quiet. had to mess with the voltage a bit to get the thermal curve right but its been running cool ever since even in summer.

on the DSP filters question -- depends what youre doing. if youre mostly SSB casual operating probably not worth the hassle. but if you work a lot of crowded CW or digital and the built in filters feel like theyre not cutting it, the Collins filters some people install make a noticeable difference on receive. the problem is finding them these days and the install is more involved than the mars mod. id say try the IF shift and width controls more aggressively first and see if you can get what you need out of the stock filters before spending money

yeah i did the MARS mod on mine years ago, same experience basically. pretty easy mod and the radio doesnt even know the difference. one thing i'll mention is double check your power output across the extended range after, mine was a little low on some of the 60m channels and needed a small tweak in the service menu. nothing crazy but worth verifying with a wattmeter before you rely on it for anything.