They were commonly used in the early '70's in audio filter applications. I think the major use for them were in RTTY demodulators designed by Irv Hoff, such as his ST-6. Jerry W4UK At 15:37 7/16/2006, Ted Huf W4ZE wrote: >A friend of mine is looking for a source for 88mh toroid loading coils. No >I don't know what he wants to do with them. > >Ted Huf >W4ZE