so ive been running my 7300 for about two years now and generally happy with it but i kept reading about the front end being a little soft on 40m especially when the band is crowded, so i went ahead and added an outboard preselector — not really a mod inside the radio itself just a bandpass filter setup i built from a design i found on qrz. that part went fine actually.

but then i got a little ambitious and started looking at the LNA mod some guys do where you swap out the input section stuff to improve dynamic range. i found a writeup on a japanese site (translated it with google which was... interesting) and went in with a soldering iron. the work looks clean under magnification but now im noticing the noise floor seems slightly higher on 80m than before and im not sure if thats real or if im just paranoid because i touched something i shouldnt have.

anyone done similar mods to theirs and have baseline numbers to compare against? i dont have an SDR to run proper measurements and im mostly going by ear which i know is not ideal. radio otherwise works fine, all bands, no weird spurs that i can hear.

the noise floor thing after poking around the front end is pretty common — sometimes its just a solder bridge you cant see or a component that got a little too much heat. i did the bandpass filter approach on my 7600 and left the internals alone after reading about what you're describing, honestly the external filtering got me most of what i wanted without the risk.

if you can borrow an SDR even a cheap rtlsdr dongle and set it up as a panadapter you can at least do a rough before/after comparison against someones published numbers online. not lab grade but enough to tell you if you're significantly off. the 7300 has pretty well documented baseline specs so you'd have something to compare to. also worth reflowing those joints if you havent already, cold solder on that kind of board is sneaky.

yeah i did a similar mod on mine based on some writeup that was going around a couple years back. honestly couldnt tell a difference either way lol. 40m is still 40m when the eu stations are all piled up at 7.074 and everyone's running 500 watts. the radio is probably not your limiting factor most of the time anyway. what antenna you running?