so ive been sitting on doing this for about two years now and finally just did it last weekend. the mars/cap mod on the ft-857d to open up the tx range. pretty straightforward once you find the right resistor to pull, took maybe 20 minutes with a decent soldering iron and some patience not to strip the tiny screws on that chassis.

honestly the main reason i did it was for some local emcomm stuff where we occasionally need to hit some non-ham freqs during exercises with the right authorization. but also just wanted to see if the rig would behave any differently on the regular ham bands after, and i honestly cant tell a difference which is probably a good thing.

anyone else done mods on the 857 specifically? theres also a mod i saw floating around about the internal fan threshold, mine runs pretty warm and the fan kicks in late it seems like. not sure if thats actually worth messing with or if ill just make it worse somehow.

yeah the fan mod is legit on that radio. the stock fan controller lets it get warmer than it probably should before spinning up, theres a resistor swap that lowers the temp threshold and it makes a noticeable difference especially if youre running any kind of digital modes for extended periods. i think i found the values on eham or maybe it was on the yahoo group archive before those all got nuked. something like swapping a 47k for a lower value but dont quote me on the exact number, you really want to look that up from a reliable source before poking around in there.

the 857 chassis is tight and thermal management was clearly an afterthought so anything you can do to help it breathe is probably worth it. mine runs digital psk and wsjt sessions and after the fan mod it stays way more comfortable to the touch during a long session.

did the same mod on mine a couple years back for similar reasons. no issues at all on normal ham operation afterward, radio didnt even notice. just be careful you dont accidentally bridge anything else when youre in there, the 857 board is pretty dense and i bumped a cap once and had a minor panic attack thinking i killed it. turned out fine but yeah go slow.