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 a huge deal obviously but wanted to share some notes for anyone on the fence about it.

the mod itself took maybe 20 minutes, its just pulling a diode on the PA board, D1821 if i remember right. you do have to get pretty deep in there which is a little nerve wracking on a radio this packed. i used a heat gun on low and was super careful around the nearby caps. came out fine.

what i actually wanted to talk about though is that i combined this with the ref osc mod - replaced the stock TCXO with a proper 0.5ppm unit i sourced from a surplus place. frequency stability on 10m and up is noticeably better, like actually noticeably, not placebo. before i was seeing maybe 20-30hz of drift after warmup on 2m, now its basically nothing after the first couple minutes.

anyone else done the osc swap on an 857 or the 897? curious if the pinout is the same or if i got lucky that it was a drop-in.

the TCXO swap on the 897D should be the same deal, yaesu used basically the same reference oscillator across that whole product line from that era. i did mine about three years ago with a morion unit and had zero issues. pinout matched exactly. only thing i'll say is make sure you're feeding it the right voltage - the stock one is 2.85v i think and some of the aftermarket units want 3.0 or 3.3, so double check your datasheet before you just drop it in. i fried one that way on a different radio and it's not a fun lesson to learn twice.

the TX mod i haven't bothered with on mine just because i dont really have a use case for it but good to know it's straightforward. might do it anyway just to have it done.

yeah the 857 is a pretty moddable little radio honestly. i did the display brightness mod on mine which sounds trivial but when you're mobile at night that thing is blinding at stock settings. just a resistor swap on the backlight circuit.

been thinking about the osc mod too but havent pulled the trigger. do you notice any difference on HF or is it really only worth it on VHF/UHF? asking because most of my operating is 40 and 20 and im not sure its worth the hassle if the drift is already small at those freqs