¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. FT-857
  2. Topics

Reduced FM sensitivity.

[email protected]
 

Recently the FM sensitivity of my 857D is greatly reduced on 2M and 440. ?I do not hear any crackling noises an those or any other bands/modes so not sure if this is the ceramic filter problem or not. ?Not sure if related but the CAT has also stopped working. ?If it is the ceramic filter could someone point me toward a fix procedure?


73, Bill NZ0T
 

Is your RF Gain/Squelch knob set too high? Been there, done that. Clockwise all the way is lowest squelch.


The CAT connection has a fuse on the 857 motherboard. Carefully check to see if you have 13.8 V on the CAT cable (see pin-out in the manual p32). If not, bad fuse. Cost is about $200 to have Yaesu fix it or you can do it yourself if you are careful.
[email protected]
 

Changing RF/Squelch made no difference and their is no voltage present on the CAT pin so guess I need to open it up and see what's going on.
 

Is the sensitivity in other modes - e.g. SSB - normal on 2m and 70 cm?? That would distinguish between a problem in the front end, or a problem in the IF.

If the sensitivity is only down in FM, not other modes, then it is possible that it is one of the FM ceramic filters.? When you switch to "narrow band FM" then a different filter is used.? So, is your sensitivity in FM down both in narrow, and normal, mode?? If the sensitivity is very different between the two positions, then you have probably found the culprit - one of the FM ceramic filters.? If the sensitivity is roughly the same in both FM modes, then it is probably not one of the FM filters.

?????????????? Good luck,
??????????????????????? 73
????????????????????????????? Darrel, aa7fv.
[email protected]
 

It's hard to tell for sure but CW/SSB on 2M/440 sounds OK to me and sensitivity is fine on those modes on all HF bands..? What is interesting is that when I first go to FM-W to listen to a broadcast station sensitivity is normal S9++ for about 3 seconds then falls off just like with FM-N.? I also noticed a white dusty looking coating on filter CF1003 when I opened the rig up.? I'm pretty sure it's the ceramic filters and guess I'll replace all three just to be safe.

Thanks for your help!

73, Bill NZ0T
 

Do the cap mod too, if needed. Depends on your year and lot number.

Mitch
N4MF
[email protected]
 

Is Yaesu the only source for these filters or can I get them somewhere else?
 

Bill,

Did you find a solution to your reduced sensitivity issue?

Thanks,

Paul, ve1dy


---In FT-857@..., <nz0tham@...> wrote :

Recently the FM sensitivity of my 857D is greatly reduced on 2M and 440. ?I do not hear any crackling noises an those or any other bands/modes so not sure if this is the ceramic filter problem or not. ?Not sure if related but the CAT has also stopped working. ?If it is the ceramic filter could someone point me toward a fix procedure?


73, Bill NZ0T

1 - 8 of 8