>>In looking on the FAIR RITE web page I see that type 43
>>material is
>>spec'd for freq range 25-300 Mhz. So why use a material
>>for that
>>range...what gives?..
>
> When you use a ferrite to wind a transformer, you want LOW
> loss.
> When you use a ferrite for suppression of RFI, you want
> HIGH loss.
> The Fair-Rite catalog is listing this as a suppression
> part, and 25-
> 300 MHz is the range where it has relatively high loss. It
> is a low
> loss part below 10 MHz, and thus a fairly good choice for
> winding
> Beverage transformers.
It really depends on the specific application. If it is a
closely coupled winding, a transmission line transformer, or
broadband transformer we generally want a core with an
impedance peak around the lowest part of the operating
frequency range. This is generally true for receiving
applications.
If it is a resonant circuit we generally want high Q, or a
low loss tangent compared to the impedance, at the operating
frequency. The same is true if the core handles high power.
If it is a suppression device we generally want high
resistance compared to reactance.
I almost exclusively use 73 materials for broadband .5 to
30MHz receiving applications.
73 Tom
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