so ive been sitting on this TCXO-15 unit for like three months now and finally got around to installing it last weekend. took me longer than it should have because i was being overly cautious with the ribbon cables but overall not a bad job if you've done any surface work before.

the thing is i'm not totally sure i can hear a difference in normal operation but on WSPR overnight the drift is noticeably better — like the signal just sits there instead of wandering around the edges. before the mod i was seeing maybe 2-3 Hz of drift over a few hours and now its basically flat. running a GPS disciplined reference on my other rig so i have something to compare against.

not sure it matters for most operating honestly. if you're doing FT8 or voice work probably not worth pulling the rig apart. but if you're into weak signal stuff or trying to run any kind of precision frequency work its a pretty clean mod and icom actually sells the part so its not like you're voiding warranty with some frankenboard situation. anyone else done this or any other internal mods on the 7300 thats actually made a real difference to them?

yeah did this about a year ago and same experience — you won't notice anything casual operating but hook it up to a frequency counter or run it against a GPS ref and the difference is pretty clear. i mainly did it because i was doing some 10 GHz transverter work and the LO stability actually matters when you're multiplying up that high. small error at HF becomes a big problem at 10 gig.

only thing i'd add is make sure you let the rig warm up for like 20-30 min before you judge the stability, the TCXO still has a warmup curve its just much tighter than stock. also while you had it open did you do anything with the TX low pass filters or mess with the bias at all? i've been tempted to touch the PA bias a little but don't want to go down that rabbit hole without a good reason.

honestly i just leave mine stock, the 7300 is already pretty decent out of the box for what most people do with it. but i get it if youre doing the wspr and weak signal stuff. my buddy did a similar mod on his 705 and swears by it for portable ops where temperatures swing around.

the one mod i actually have done is the simple fan mod where you swap in a quieter fan because the stock one drove me nuts in a quiet shack. not exactly performance but quality of life improvement for sure.