John KD5YI wrote:
Using your argument, I could buy an inductor wound on a toroid core and
claim it is a "distributed" component because it "electrically" replaces
some calculated "degrees" or "feet" of wire at some frequency.
Sorry, that's not true. Toroidal inductors are not covered
by my argument adopted from Dr. Corum's IEEE paper. Toroidal
inductors are not being discussed at all - except by people
afraid to discuss large air-core loading coils. My argument
(based on Dr. Corum's assertions) apply *only* to large,
air-core coils that meet the conditions listed on page 4 of
Dr. Corum's paper at:
http://www.ttr.com/TELSIKS2001-MASTER-1.pdf
A 75m Texas Bugcatcher coil is an example of the type
of air-core loading coil that I am talking about. It's
about 6" diameter, 4 tpi, and 6.75" long. Dr. Corum's
equations indicate a VF of ~0.02 for such a coil used
on 4 MHz which makes it electrically about 28 degrees
long.
You appear to be trying to make lumped components into distributed
components to suit your arguments. Shame on you.
No, just the opposite. I am trying to keep others
from considering large air-core distributed network
loading coils to be lumped components (which they
obviously are not). Dr. Corum says any coil electrically
longer than 15 degrees (0.04WL) needs to be treated
as a distrubuted network, not as a lumped-circuit.
Here are some of Dr. Corum's class notes:
http://www.ttr.com/corum/index.htm
Here's a quote: "In the following note, we will show
why one needs transmission line analysis (or Maxwell's
equations) to model these electrically distributed
structures. Lumped circuit theory fails because it's
a *theory* whose presuppositions are inadequate. Every
EE in the world was warned of this in their first
sophomore circuits course."
Yet W8JI reports a 3 nS delay through a 100 turn, 10"
long, 2" dia loading coil on 4 MHz, an obvious
impossibility since such a large, long air-core inductor
is nowhere near to being a lumped-inductor. At ~37
degrees, based on Dr. Corum's equations, it is more
than double the 15 degrees that is the point at
which the lumped-circuit model starts to fail.
37 degrees gives a delay of ~25 nS on 4 MHz. That's
approximately what one would measure if one used a
traveling wave for the measurement instead of a
standing wave (which doesn't change phase with
distance). W8JI's "measurements" were off by almost
a magnitude.
--
73, Cecil, IEEE, OOTC,
http://www.w5dxp.com