so ive been messing around with the mars/cap mod on my 857D to open up the tx range a bit and while im at it figured id do the extended receive mod too, pretty straightforward solder jumpers on the main board deal. followed the instructions from the mods.dk page and a couple youtube vids that all seemed to agree on which jumpers to cut/bridge.

everything went fine i think, tx seems to work on the extended freqs and receive is definitely opened up which is great for wideband listening. but now on 10m specifically around 28.4 or so it seems like the noise floor has gone up a bit? like maybe 2-3 S units worth of what just looks like broadband hash. doesnt happen on other bands at least not that i can tell. was wondering if anyone else ran into this after doing these mods or if i maybe bridged something i shouldnt have. havent checked all the jumper positions against the service manual yet, thats my next step i guess but thought id ask here first.

radio is stock otherwise, no other internal mods. running it into a hexbeam so the antenna side should be fine, this is definitely something in the radio itself.

yeah the extended rx mod on those radios can sometimes affect the front end filtering a bit depending on which revision board you have. yaesu made a few changes over the production run and not all the mod guides account for that. check what board revision yours is - theres usually a sticker or marking near the main board, something like rev C or D etc. some of the jumper maps floating around online are for earlier revisions and if you apply them to a later board you can end up with slightly different results.

the 10m noise thing is interesting though, 28mhz is right where some of the switching artifacts from the PLL can creep in if the filtering isnt quite right. id go back and double check JM1001 and JM1002 positions against the actual service manual for YOUR specific revision, not just a generic mod page. the mods.dk stuff is good but its aggregated from a lot of sources and sometimes the details get muddled. if you have a service manual PDF check section 7 or 8 depending on your version, the jumper table should be in there with the factory positions clearly marked so you can verify everything is where it should be.

i did basically the same mod on mine couple years ago and didnt have that problem but mine is an older unit so maybe different board. one thing i did notice is that after opening up the rx i started hearing a ton of stuff i wasnt hearing before, some of it looks like noise but its actually just garbage that was always there and the filtering was keeping out. might be worth taking the radio somewhere else or trying a different antenna just to rule out that its not local interference youre suddenly hearing because you opened up the passband a little. just a thought, could be totally off base but worth checking before you start poking at the jumpers again