On 4/17/2012 2:05 PM, Steve Hunt wrote:
> I am trying to understand
> why you would label a choke "And it's _Inductive!_ (Bad)", whose
> Resistive component is greater than its Reactive component over the
> large majority of the HF spectrum.
An important difference between my view and yours is that I think, and
look at plots, with a log frequency axis, and so does mother nature.
160M, 80M, and 40M are very important bands to me, (and some guys like
to work 60M). On a log basis, those four bands ARE more than half of our
spectrum below 30 MHz, and #31 cores are NOT predominantly resistive
below 10 MHz! (The word "predominantly" means to me that the impedance
is significantly more resistive than inductive, not within 20-30% of the
same, and even with #31, resistance is still only 20-30% greater than XL
between 7 and 15 MHz for most sizes of cores.
Looking at 0431167281, a clamp-on part that fits RG8. R and X are equal
at about 7 MHz, and remain approximately equal to about 15 MHz. To get
5,000 ohms resistive on 160M I would need 250 of these cores, for 80M I
would need 200 of them, and for 40M I would need 100. A solid cylinder,
2631626302, behaves quite similarly.
Also, note that the resistive component of the impedance of #43 does not
become equal to the inductive component until you hit about 18-20 MHz,
depending on the size of the part.
73, Jim K9YC
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