so ive been sitting on this for a while but last weekend i finally cracked open the 857d and did the transmit mod to open it up past the ham bands. not that i actually needed it for anything specific, more just wanted the option and i was already in there messing with the squelch pot which had gotten scratchy as hell over the years.

while i had it open i also did the ref oscillator mod with a TCXO replacement, grabbed a cheap-ish one off ebay that supposedly drops the frequency error down to under 0.5ppm. haven't done a proper calibration against a GPS disciplined source yet so i cant really say how much difference it made but the display reading seems more stable on 10m compared to before. probably placebo but who knows.

also replaced the stock electrolytic caps near the final amp section since a couple looked a little puffy to me. radio is like 15 years old at this point so figured it couldnt hurt. anyone else done any of these mods or have opinions on whether the TCXO thing is actually worth the trouble? i feel like for HF its probably overkill but on 2m/70cm it might actually matter

the TCXO swap is worth it imo, especially if you do any weak signal stuff on vhf/uhf. i did the same mod on mine maybe 3 years ago and the difference on 2m SSB was noticeable, at least compared to what it was before which was drifting annoyingly after warmup. on HF yeah probably doesnt matter much, a few hz off on 40m nobody cares. but if you ever get into any digital modes on the higher bands that require tight frequency accuracy it starts to matter more than you'd think.

good call on the caps btw. i did a recap on an older FT-817 and found two that were measuring way outside spec even though they didnt look bad visually. the puffy ones you caught were probably already causing some compression issues near the finals.

yeah i did the mars mod on mine years ago, pretty straightforward on that radio. the only thing id say is double-check your SWR before you actually transmit anywhere outside the ham bands cause the lpf sections arent really optimized for everything in between and you can get some weird harmonic stuff depending on the frequency. probably not a big deal at qrp levels but worth knowing.