so ive been putting this off for like a year because i kept reading conflicting stuff online about whether it was worth doing and whether it would mess with anything else. finally just did it last weekend. for anyone who hasnt done it, its literally just opening the radio, locating the right connector inside, and either removing a jumper or bridging two points depending on your firmware version — takes maybe 20 minutes if you go slow.

the main reason i wanted it was to get TX outside the ham bands for some MARS work and also just to have the flexibility when im experimenting. the mod itself went fine, no issues there. but here's the thing nobody really talks about — after you do it, the ALC behavior feels slightly different to me on the edges of the extended range. might be totally psychosomatic honestly, i dunno. the SWR is fine, everything reads normal, but something just feels off about the way the power ramp up at 29.7 MHz. could just be my antenna being less happy up there.

anyway if anyone else has done this on the newer firmware versions (mine was on 1.40 before i updated) id be curious if you noticed anything weird or if im just imagining things.

did the same mod on mine probably two years ago now, running 1.30 at the time. honestly didnt notice anything weird with the ALC but i wasnt specifically looking for it either. the power output does taper a bit naturally past the band edges just because the LPF switching and the finals arent optimized for those freqs — thats by design really, not a mod artifact. icom tunes those stages for the ham bands so anything outside is gonna be a little less linear. wouldnt worry about it unless you're seeing actual distortion on a spectrum analyzer or your IMD numbers look bad.

one thing i will say is after the mod i went ahead and also did the ref clock modification, swapped in a TCXO for better frequency stability. that one made a much more noticeable real-world difference than the MARS mod honestly. if you havent done that one yet its worth looking into, especially if you do any weak signal digital modes.

the ALC thing you're describing is real imo, not in your head. i noticed something similar on my 7300 around 29-30 MHz range after the mod. what i think is happening is the radio's protection circuitry gets a little more conservative when its operating in ranges it wasnt expecting to, kind of like it knows it shouldnt be there. total speculation on my part but it tracks with what i've seen. doesnt cause any actual problem in practice, at least not for me.