so ive been putting this off for like a year but finally cracked open the IC-7300 last weekend and did the extended transmit mod. pretty straightforward honestly, just the two diodes on the main board, took maybe 20 minutes once i had it on the bench with good light. now i can hit the MARS/CAP frequencies no problem which is the whole reason i did it.

what i wasnt expecting is how much i ended up down the rabbit hole after that. started looking at the bandpass filter mods people have been doing and also saw some stuff about the ref oscillator replacement for better frequency stability. the TCXO upgrade looks interesting but im not sure its worth the cost for how i actually use the radio — mostly ragchewing on 40 and some digital on 20. like if i was doing serious weak signal stuff or FT8 contesting maybe, but for casual use i dunno.

anybody done the ref oscillator swap on these? and also curious if anyone has messed with the audio filtering at all, i feel like the SSB rx audio could be a little less harsh on mine but that might just be my ears and the antenna situation more than anything with the rig itself.

did the same diode mod about 8 months ago, no issues. one thing i'd say is double check your solder joints on those pads because mine had one that looked fine but was actually a cold joint and i had intermittent TX issues for a week before i figured out what was going on. reflowed it and been solid since.

on the TCXO thing — i actually did do that upgrade and honestly for FT8 it does make a difference, you can see it in how tight your signal looks on the waterfall compared to before. but like you said if youre just doing phone operation its probably not something youre gonna notice day to day. the ref oscillator in the stock 7300 isnt bad, its just not great if you care about that last bit of frequency accuracy.

havent touched the audio filtering, my approach with that radio is just to use the built in DSP settings and call it a day. the twin PBT and the notch filter do a lot of the heavy lifting already.

yeah the audio thing on mine bugged me too for a while and i eventually just started running it into a little outboard equalizer and that helped more than i expected. probably not what you want to hear if youre looking for an internal fix but its an option. someone on one of the other forums posted about tweaking the IF filter bandwidth settings in the menu and that did clean things up a bit for me on crowded band conditions — not really a mod just playing with whats already there but worth messing around with before you go opening it up again.