so ive had my 857d for about 3 years now and just recently found out about the extended receive modification where you open it up and move a couple diodes to unlock the wider rx coverage. been reading different things about it and some people say its totally fine and others act like youre going to blow the radio up or void some critical warranty which honestly at 3 years old i dont really care about the warranty anymore.

what i actually want to know is whether the mod genuinely improves anything practical or if its more of a curiosity thing. i mostly do HF and some 2m/70cm but i do like scanning around and monitoring stuff outside the ham bands occasionally. the receive sensitivity supposedly drops off outside the normal coverage but how bad is it really, like is it unusable or just slightly worse. also has anyone done the mars/cap mod at the same time, seems like you might as well do both if you already have the case open.

not really looking for a lecture about regulations or whatever, just practical experience from people who have actually done it

did both mods on mine maybe 18 months ago, the extended rx and the mars/cap at the same time. honestly the hardest part was just not losing the tiny diodes when i moved them, tweezers and good lighting are your friends. the rx outside normal coverage is definitely degraded, like youre not going to be pulling in weak signals on 118 MHz airband or whatever with any reliability, but for strong local stuff it works fine. i mostly use it to poke around the 60m area and listen to some utility stuff and for that its perfectly adequate.

the mars/cap tx mod is the one i actually use more, being able to transmit slightly outside the band edges has been handy a few times during nets that use those edge frequencies. just make sure you grab the right service manual for your specific version of the radio because there were a few hardware revisions and the diode locations moved around between them. W4RT used to have a good write-up on it.

yeah the rx sensitivity falloff is real but honestly for anything stronger than like a marginal signal you wont notice. i checked mine with a signal generator after doing the mod and you lose maybe 15-20dB on the far edges of the extended range compared to in-band, which sounds bad but most things youre going to want to listen to outside the ham bands arent exactly weak. airband comms, weather, shortwave broadcasts, all fine.

one thing i'll add that nobody ever mentions is make sure you take photos before you move anything because putting it back stock if you ever sell it is a pain if you cant remember exactly which pads had diodes and which didnt. ask me how i know lol