so ive been sitting on doing the mars/cap mod on my FT-857D for probably two years now, always talked myself out of it because i was worried about messing something up. finally just did it last weekend and honestly it was way less scary than i expected. the jumper is right there once you open the bottom panel, took maybe 20 minutes including the time i spent double checking the service manual three times like a nervous wreck.

anyway the reason i actually got around to it is i wanted to experiment with some of the 60m channels and also just generally wanted more flexibility without having to think about it. transmit works fine across the extended range, power output seems consistent, no weird behavior on the bands i normally use. i did notice the fan seems to kick on a little earlier now but that might just be me paying more attention to it after poking around inside the radio.

what i really want to do next is the high stability TCXO option but those seem hard to source now. anyone done the TCXO-9 upgrade recently and know if theres still a reliable place to get one? my understanding is it drops the frequency stability from like 5ppm down to 0.5ppm which would actually matter for weak signal stuff on 2m. also been reading about people doing filter swaps on the 857 for better SSB audio but im not sure if thats worth the hassle on a radio this size

the TCXO-9 sourcing situation is genuinely annoying. i got one from a seller on one of the japanese surplus electronics sites a while back but that was a few years ago and i have no idea if they still have stock. might be worth checking the usual suspects on ebay but watch out for counterfeits, had a guy in our club get burned on a fake one that was way off spec. yaesu themselves used to be a reasonable source but good luck getting anything out of their parts department these days.

on the filter thing though, i did the 500hz CW filter in mine and it made a noticeable difference on crowded contest weekends. the SSB filter swap is a bit trickier because you really need to think about which filter slot youre putting it in and what youre giving up. some people go with a 1.8khz collins mechanical but honestly i found the stock 2.3khz is fine for casual SSB and the real improvement came from just tweaking the IF shift and width controls more carefully. your mileage may vary obviously

yeah the mars mod on that radio is pretty straightforward, did mine ages ago. one thing worth mentioning is make sure you reseat the bottom panel connectors properly when you close it back up, i had a buddy who got intermittent issues on VHF for weeks after doing that mod and it turned out one of the ribbon connectors wasnt fully seated. minor thing but worth checking.