so ive been putting this off for like two years but i finally cracked open the 857D last weekend to do the extended TX mod. you know the one where you move the diodes on the main board to open up the transmit range. wasnt as scary as i thought honestly, just needed a steady hand and decent soldering iron. i used my Hakko and it went fine.

anyway the reason i finally did it is i picked up an EMCOMM deployment kit from the club and they wanted the radio to be able to hit MARS/CAP frequencies so that was the push i needed. got my MARS license sorted a few months back so its all legit.

what i didnt expect was how much the mod also seemed to improve receive on some of the upper HF bands, or maybe im just imagining things. could be placebo. the radio does feel a bit more responsive on 10m but i have no way to actually measure that so take it with a grain of salt.

anyone else done this and noticed anything weird after? also debating whether to do the Collins filter mod next, ive heard that makes a real difference on SSB but also ive heard it makes almost no difference depending on who you ask.

yeah the diode mod on those Yaesus is pretty standard at this point, been doing it on 857s and 897s for years. you almost certainly didnt change the RX characteristics, the TX and RX paths are separate enough that moving those diodes shouldnt touch anything on the receive side. probably just confirmation bias after doing the mod, which is totally normal lol.

on the Collins filter question -- it depends what youre doing with the radio. if youre running it mostly mobile or in noisy environments, the stock DSP filtering in the 857D is honestly decent enough and the collins filter wont blow your mind. but if you sit at a desk and do a lot of CW or work crowded SSB pileups, yeah you'll notice it. i put one in mine about three years ago and it made a real difference in CW selectivity, less so SSB but still noticeable. the mod itself is dead simple compared to the TX thing, its just dropping the filter into a socket. just make sure you get the right part number, theres a couple variants floating around and not all of them fit right.

the MARS angle is what finally got me to do the same mod on my 817 years ago. club coordinator basically said either do it or bring a different radio and that was enough motivation. went fine, just double check your work before you key up on anything outside the ham bands obviously.

i wouldnt overthink the collins filter unless youre genuinely chasing weak signals or contesting. for emcomm stuff the stock radio is fine.