On 4/5/2022 4:21 PM, Gary Johnson via RFI wrote:
A secondary choice is a 1.4-inch mix 41, Fair-Rite 2643802702. Those are in
stock.
#43 material is not great for use at HF because of their wide
manufacturing tolerances and relatively high Q as compared to #31. The
difference is that #31 is MnZn, which has both circuit resonance (the
winding) and dimensional resonance. The two combine to provide a much
broader resonance. While #31 also has comparable wide mfg tolerances,
the broader resonance makes predictable designs possible. #43 is NiZn,
which has no dimensional resonance, thus higher Q.
I didn't come to this conclusion until I did the extensive research that
led to the 2018 Cookbook.
73, Jim K9YC
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