so ive had this 857 for about 6 years, bought it used and it's been rock solid until maybe a month ago. started noticing weak signals on 20m that i was previously hearing just fine, at first i thought it was band conditions but its definitely the radio. checked the antenna with my analyzer and SWR looks normal, tried a dummy load just to rule things out and the issue persists. transmit power on all bands reads what it should on my wattmeter so the PA seems okay.

the weird part is HF is noticeably worse but VHF/UHF on the same radio seems about the same as it always was. like 2m sounds fine. so im thinking its something in the HF receive chain specifically. i poked around a bit looking for anything obviously wrong, no burnt smell, no visible component damage. havent touched the front end yet because i dont want to make things worse without a plan.

anyone dealt with something like this on a 857 or similar yaesu? wondering if the RF amp stage or maybe one of the band pass filter relays could be the culprit. i have a decent bench setup, analog and digital meters, soldering station, but im not experienced enough to know where to probe first without a schematic roadmap.

had almost the exact same symptom on a 897 a couple years back, turned out to be a front end relay that wasnt switching cleanly. the HF receive path goes through those T/R and band relays and if one of em gets corroded contacts or the coil is pulling weak you'll get exactly what you're describing — tx fine because that path bypasses the relay, rx is degraded because it goes through it. yaesu service manuals are floating around on the usual sites and they have the relay locations marked. worth putting a signal generator on the antenna port if you have access to one and just measuring what's actually getting through versus what should be. if you dont have a sig gen even just a known signal like WWV on 10 or 15 mhz and comparing it to a second radio on the same antenna via a splitter can at least tell you how far down you are in dB terms.

also worth checking the IPO/ATT button settings havent gotten toggled somehow, i know that sounds dumb but ive seen people chase ghosts for a week over that.

the relay theory is pretty solid, that's where i'd look first too. one thing i'll add — on the 857 specifically there's been some talk on eham about the SMD capacitors in the front end going leaky over time, especially on older units that ran hot. not super common but worth keeping in mind if the relay checks out okay. the service manual for the 857 is honestly pretty good once you find the right version, there were a few revisions. if you can get a signal tracer or even just a cheap RTL-SDR to inject test signals at different points in the chain you can usually narrow it down pretty fast without just swapping parts blind.