Tuner question

I have a Rotel RX-850a receiver (in my kids playroom) as a 2nd system with an exterior roof mounted Magnum Dynalab antenna. I have been enjoying fantastic FM until recently. Lately some of the stations have significantly reduced signal strength and one or two have to be on mono to be heard. I plugged the antenna lead into a Tivoli radio and the problem doesn't seem to be the antenna, as the reception seems quite strong accross the dial. Does my problem seem like it could be the tuner in the Rotel? I find it curious that some sations are suffering more than others. Any thoughts are appreciated.
I suspect your problem may be in the tuner, but FWIW....

Some stations broadcast stronger signals than others but the signals may still be pegged on the signal meter in your tuner. So prior to your problem they were all sufficiently high to max out your tuner's needs, now you are seeing the differences in the different signal strengths.

Other possibilities to consider. The fading stations themselves may have reduced their power output. That happened to me a few years ago and my favorite station is now good (noise free) only in mono. Another possibility is that the stations broadcast antenna may have been relocated to a place more distant from your house.

BTW I have a little Tivoli on my desk (mono) and it is amazing how it pulls in the weak signals. Compared to other desk top radios anyway.

Also, if the signal is weak, but otherwise clean, you might for some reason have some problems with cable and or connections/connectors on your antenna. Especially the outdoor connections. Check them out to make sure you don't have rusted wires etc. The more I think about it, the more this possibility appeals to me.

Also, on occasions I have used a 10db amp placed near the antenna and got good results by simply boosting signal strength.

Hope that helps you a bit.
LOL, I just experienced the same problem! An accross the board substantial reduction in signal strength and many marginal stations now do not appear at all. My Tivoli works fine!

I found my problem was a bad connection with the 75ohm cable at the tuner imput. Put in a new cable. Problem solved. :-)
small world. I borrowed another tuner and tomorrow I'll be able to isolate if it is my antenna or receiver that is having the problem.