Hi Frank, In fact, the Icom 9 MHz filters (and the high-IF roofing filters) are monolithic crystal filters (MCF), whilst the 455 kHz filters such as the FL-44A, FL-52A etc. use discrete crystals with matching networks. Cheers for now, 73, Adam VA7OJ/AB4OJ Scanned by WinProxy http://www.Ositis.com/