> I used an R in the load of 2 ohms for the small L value, and 4 ohms for
> the large.. Im a bit vague as to what to put there for real world stuff..
The most detailed and accurate loading inductor text readily
available to amateurs appears in the chapter "Reactive Elements
and Impedance Limits" in Kuecken's book "Antennas and
Transmission Lines" now reprinted by MFJ. I was introduced to this
book in the early 70's while taking a course on antennas.
I've measured hundreds of inductors. A typical B&W miniductor or
Airdux coil of #12 wire operated far from self-resonance with a form
factor of 2:1 L/D has a Q in the 300 range. Optimum Q almost
always occurs with bare wire space wound one turn apart, but
optimum L/D can range from .5 to 2 or more depending on how far
below self-resonance you operate the inductor and what is around
the inductor and how big the conductors in the coil are.
Large optimal edge-wound or copper tubing coils can get into the Q
~800 range. I've never in my life seen an inductor of reasonable
reactance above that Q, and very few make it that high. When I
test inductors with Q's of several hundred, I have to use a large
copper box and keep my hands and body far away from the coil or I
actually see the Q drop!
If you take the inductive reactance in ohms and divide it by 250-
350, that would be a reasonable estimate of ESR assuming the
inductor is reasonably well designed and operated far below self-
resonance. As you approach self-resonance Q drops like a rock in
this application, since the final system is series-resonant.
> have a 78 uh bugcatcher coil that has a .5 ohm resistance and a hi gain
> that is close in L that has 3 ohms resistance. So based on the past
> discussions on rf resistance being a different animal, I hope I used the
> correct values.
You have 900 ohms reactance. An air wound coil of reasonable
size wire as described above would have an ESR of about 3 ohms.
Good work!
If the wire is insulated (even with teflon) and close wound, Q can be
about half that. If it is especially good twice that. So a range of 1.5
to six ohms would cover it. (Litz wire will make it Q~150 ESR 6
ohms most likely, and small copper tubing or #6 or 8 solid wire
about 1.5 ohms).
> At any rate the results seem to show even if the cap hats droop they are
> still better thanjust using L.
No doubt. The results are even more profound over excellent ground
systems!
73, Tom W8JI
W8JI@contesting.com
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