[Elecraft] Toroids

[Mychael Morohovich AA3WF]

Edward wrote, " Is this what I might expect ? Or is their actually something
wrong with my toroids ?"


Hi, Edward-

If you check the inductance of toroids on your own meter, please note that
some of the values specified in the Elecraft manuals may vary and that
differences in individual inductance meters often increase this variation.
Elecraft recommends that individual builders do NOT try adjusting their
coils to the exact values shown in the manual.

Keep in mind that ferrite cores (such as the FT37-43 core used for KNB2-L3)
can vary in value by 50% or more, depending on the exact mix. Ferrites tend
to be used for constructing HF broadband transformers and rf chokes where a
range of inductance, rather than an exact value, is considered acceptable.
FWIW,  L1 and L2 of the KNB2 consistently measure 1.2 uH on my meter. L3
varies from 55-90 uH.

In the thousands of toroids I have shipped out, only a few powdered iron
cores have been off by enough that adjusting the windings wouldn't budge the
L-value sufficiently to put them within spec. In other words, if you use the
correct cores and wind to the proper specifications, you should be in good
shape.

Happy Building!

Mychael AA3WF
K2# 1025