so ive been sitting on this for a while but last weekend i finally pulled the trigger and did the mars/cap mod on my FT-857D. honestly wasnt that scary once i got the thing open, just moving a couple diodes, but man it took me forever to find a decent set of photos that matched my specific board revision. half the guides online seem to be for older units and the jumper locations are slightly different.

anyway now i have TX down into 136khz territory which i probably wont ever use but its nice to have i guess. the main reason i did it was to work some frequencies for a local ARES group that needed us to cover some commercial bands during drills. the radio seems fine, no issues so far, hadnt noticed any sensitivity changes on RX either which i was a little worried about.

has anyone done the deviation tweak on these as well? im thinking about bumping the FM deviation slightly because it sounds a little narrow on local repeaters compared to my other rigs. or maybe thats just how this radio is idk

yeah the board revision thing is real, i burned like two hours comparing my unit to some youtube video before realizing the guy had an older version. the diode locations are close but not identical and you definitely dont want to lift the wrong pad on that board.

on the deviation question — i did mess with that on mine. theres a service menu you can get into, i think its hold the a/b button during powerup or something like that, been a while. there are pots on the board too but the menu approach is a lot less scary. mine was set conservatively from the factory and bumping it a little made a noticeable difference on the local machine. just dont go overboard or youll start getting complaints about overdeviation which is worse than sounding a bit thin.

i did the same mod last year for the same reason, ARES stuff. works fine and i havent had any problems. one thing i'll say is just make sure you're not transmitting out of band by accident since the radio wont stop you anymore, easy to do if you fat-finger a frequency. learned that the hard way during a net when i was fiddling with VFO and ended up way off where i meant to be. nothing bad happened but it couldve.