8-Pole QER Crystal Filters

Click on photos to enlarge

Some would say a crystal-based IF filter is the very heart and soul of a good SSB rig. There’s no doubt that a clean, ripple-free and narrow-skirted “xtal” filter is essential for excellent performance, especially in a receiver. They are, however, among the most difficult builds for a home-brewing amateur to pull off. Among the easiest types, though are quasi-equiripple designs that do require using xtals closely-matched in resonant frequency (within 50Hz, but the closer the better), but that do not require the careful measurement of “motional parameters” or ESR. More on QER crystal filters can be found in recent (since at least 2011) editions of the ARRL Handbook.


Schematic Diagram (PDF)

Github Repository

PC board only $4.95 Soon on eBay Soon on Tindie
Kit of PC board, matched crystals, associated capacitors, transformer toroids, and magnet wire AVAILABLE SOON!
Fully designed, assembled, and tested AVAILABLE SOON!