I brought my Famicom out of the attic and dusted it off. Everything worked (except the Disk System, but that's another story), but I noticed the picture quality has been getting increasingly worse every time I use it. This time the picture was shaking and flickering in game for all my games. At one point, during Super Mario Bros, I was picking up a local FM station. I was wondering if anyone knew why the quality is bad and if there is any way to increase the quality.
Sounds like it's unmodded original Famicom, is so then it's just the limitation of the technology and the fact that it has been designed for Japanese frequencies. If it has been unused for several years maybe radio inteference has been increased in your area and/or capacitor and other components are showing signs of failure.
I figured it might just be this old thing. At least it still works.
try to change capacitors :)