RFI Help

[Richard VE3OZW]

Well, none of the toroids, beads or snap-ons from Palomar, Amidon, MFJ, Mouser ....  etc etc, that I have bought are marked on the ferrite itself, just on the packaging.  The commonly-available ones are all made by Fair Rite I believe, who does not mark them for identification.  I got a silver permanent Sharpie at Staples (they didn't have white, but they do have gold if you prefer) to mark them with.  Ferrites are also made by Magnetics & are colour coded, but they aren't sold by the major ham vendors.

Commonly-available powdered iron toroids are made by Micrometals & are colour coded (mix 2: red, mix 6: yellow, etc).

If you have some unknown ferrites, a procedure posted on QRZ is to:
- wind some turns (e.g. 10) of magnet wire on it
- measure the inductance (helps if you have an LC meter!)
- calculate AL (mH/1000 turns): either download Mini Ring Core Calculator http://www.electronicecircuits.com/elect...or-program, or do the math by hand
- compare with AL values for various mixes (Palomar & Amidon websites) to find a match

73
Dave, VE3WI

I do the same with my torroids to know which mix each of them are.  I do not have too many in use here, but I do have them installed on my USB cables to between my laptop and my radios as a precaution to eliminate any RFI potential. I have several of the snap ons, but have read that they do not work as well as the larger torroid rings with the proper mix.