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+---- Thread: RFI Help (/showthread.php?tid=442)
RFI Help - VE3WI Dave - 2021-04-15
Got a couple of ferrite items from Palomar Engineers. They included a useful tip sheet on combatting RFI. It may be useful if you have an RFI problem to beat. Scanned copy attached.
73
Dave, VE3WI
RE: RFI Help - VA3KOT John - 2021-04-16
That pdf is very helpful, thanks Dave. Maybe I should buy from Palomar in future because all the snap on ferrites I have bought in the past do not identify the mix being used.
RE: RFI Help - VE3WI Dave - 2021-04-16
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/electronic-software/mini-ring-core-calculator-program, or do the math by hand
- compare with AL values for various mixes (Palomar & Amidon websites) to find a match
73
Dave, VE3WI
RE: RFI Help - Richard VE3OZW - 2021-04-17
(2021-04-16, 10:43:21)VE3WI Dave Wrote: 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.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.
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/electronic-software/mini-ring-core-calculator-program, or do the math by hand
- compare with AL values for various mixes (Palomar & Amidon websites) to find a match
73
Dave, VE3WI