so i've had my FT-857D for a few years now and always heard about the mars/cap mod to open up the TX range and i finally just did it last saturday. the whole thing took maybe 20 minutes once i had the radio apart which honestly was scarier than the actual mod. just that one diode removal and boom, transmits well outside the ham bands now.

not that i'm gonna use it outside the bands obviously but i do some emcomm stuff and our served agency has some freqs that are technically outside normal allocation so it's nice to have the flexibility. the radio itself seems to work exactly the same, RX is fine, TX power output looks the same on my wattmeter. no weird issues or anything.

i also went ahead and replaced the stock fan while i had it apart because i'd read that the thermal management on these isn't great when you're running digital modes for extended periods. used a slightly higher CFM 12V fan and it does seem to run cooler when i'm doing JS8Call or Winlink for a while. that part felt more actually useful than the TX mod honestly.

anyone else done mods on the 857 or similar rigs? curious what other upgrades people have found actually make a noticeable difference vs stuff that sounds cool but doesn't really change anything in practice

the fan mod is one of the best things you can do for those radios if youre doing any kind of sustained digital operation. the stock thermal design was clearly built around SSB duty cycles and just doesnt cut it for WSPR or FT8 running all night. ive seen a few of these come through the shop with burned finals that probably could've been avoided with better airflow.

on the TX mod i'm a little more mixed. practically speaking yeah it's useful for emcomm scenarios and a lot of guys do it. just make sure your PA matching is actually optimized for whatever out of band freq you end up using because the 857 isn't flat across a wide range — you can lose a meaningful chunk of power on freqs the finals weren't tuned for. probably not a big deal for 10-20 watts out but worth knowing.

i did the ref osc mod on mine a while back, tweaked the TCXO trimmer for better frequency accuracy. the stock calibration on a lot of these mid-range Yaesu's is honestly pretty sloppy if you check it against a GPS reference. made a noticeable difference for weak signal digital modes where you're hunting around in a narrow passband.

yeah i did basically the same fan swap on mine two years ago and it's been solid. also added a small heatsink to the PA transistors while i was in there, some guy on eham had a writeup on it. not sure it does that much but it made me feel better lol.

one thing i'd suggest if you havent already — the audio mods. theres a pretty well documented mod to improve the rx audio filtering on the 857, involves swapping a couple caps in the audio chain. reception on weak SSB signals genuinely improved for me. not a huge deal if you're mostly doing digital but for voice it was noticeable enough that my wife who also has a ticket commented on it which i took as a good sign.