so ive had my 857 for about 3 years now and never bothered with the mars/cap mod or the extended receive thing but lately ive been thinking about it. mainly because i want to listen down into the lower HF stuff without swapping radios. i know you pull D42 and theres a few other jumpers or resistors depending on the version of the board you have, some of the older ones are different than the later production runs which is annoying.

anyway has anyone actually done this and noticed any real world difference in sensitivity below the ham bands or is it kind of meh. i know the front end isnt really optimized for that range so maybe its not even worth the hassle of cracking the case open. also while im in there i was thinking about the mic gain mod too, mine always felt like i had to crank the internal mic gain way up to get decent audio reports. is that a separate thing or do some people just do it all at once.

not worried about the warranty obviously its like a decade old radio at this point just want to know if its actually worth doing or if im going to get mediocre performance anyway

did the D42 pull on mine probably 2 years ago. honestly the extended rx is usable but you're right that the front end starts getting a bit deaf and overloaded depending on band conditions. around the 11 meter area its fine but if you go much lower than that you notice the sensitivity drops off. still handy if you just want to casually monitor something without dragging out a dedicated rx radio.

the mic gain thing is totally separate, thats a different spot on the board. there's a trimmer pot near the mic input circuit and you can tweak it to bring the gain up a bit. i found a decent writeup on one of the Yaesu mod sites, think it was on mods.dk or somewhere similar. made a noticeable difference for me on SSB, got better reports. just go slow with the trimmer, tiny adjustments matter a lot there.

yeah i did both mods on my 857 when i first got it used. the extended rx is whatever, i use it occasionally to check some utility freqs but its not gonna replace a proper SDR or a dedicated communications receiver. if your main goal is better HF monitoring id honestly just grab a cheap rtl-sdr and call it a day, way less risk to the radio and you get a waterfall display which is actually useful.

the mic gain mod though i thought made more of a difference than i expected. my audio was always a little thin sounding and after the mod people stopped asking me to speak up. worth doing imo if youre already comfortable taking the lid off.