Generally, Mix 43 and Mix 77 are the best for attenuation in the HF and low
VHF frequencies. For more information, check the Amidon site at:
http://www.amidoncorp.com/aai_ferritecores.htm
Although they are not cheap, I have had excellent results with the FT-240-43
cores, and I would expect that the FT-240-77 cores would work very well at
HF also, especially the lower HF bands.
Ron N6IE
www.N6IE.com
>
> For RF filtering, ferrite with a much higher permeability (and loss at
> HF) is preferred to what one would use for a transformer core at the
> same frequency. Essentially the higher the permeability the better so
> long as the DC or LF current in the wire doesn't saturate the core and
> kill off that HF loss.
>
> --
> 73, Jerry, K0CQ,
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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