/diy/ - Do It Yourself

>>1336123
>you don't want capacitors in tuned circuits drifting due to temperature variations
That's not the major issue with x5r/x7r/y5z capacitors in tuned RF circuits.
These are usually extremely non-linear devices, the capacity can drop about 10 times at rated voltage. Non-linear capacity-vs-voltage characteristic implies there will be extra frequencies generated in RF circuits, basically filters would generate "new"/extra signals on their own. Also these kinds of capacitors are usually pretty lossy devices (low Q).

https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527

BTW same applies to various magnetic materials, like ferrite or various powdered iron mixes. If you want to build high-dynamic range filter/preselector you have to use big cores (or use no core at all). Surely the receiver must be balanced, there is no need to have super-filters if mixer/IF/LO are not to par.