Cecil Moore wrote:
John Popelish wrote:

... I see no reason to assume the transmission line method (delay
independent of frequency) strictly applies. It might, but it would
take more than you saying so to assure me that it is a fact.


Assume the environment of the coil is fixed like the variable
stinger measurement I reported earlier. Besides the frequency
term, the phase constant depends upon L, C, R, and G as does
the Z0 equation. Why would the L, C, R, and G change appreciably
over a relatively narrow frequency range as in my bugcatcher coil
measurements going from 6.7 MHz to 3.0 MHz?

We are not talking about L, C, R, or any other inherent property
changing with frequency. We are talking about the delay of a current
wave in a single direction (anybody have a pair of directional coupler
current probes?) through a complex component that has several
different mechanisms that contribute to the total current passing
through it. It is the vector sum (superposition) of those current
components that is in question. Over a narrow frequency range, it is
conceivable to me, that the phase (delay) of that sum might shift,
dramatically, though any component of that sum might change its
magnitude only slightly (no faster than in proportion to the
frequency), and the phase of that component might change not at all.

And I didn't mean to imply that the delay is "independent" of
frequency, just that it is not nearly as frequency dependent
as Tom's measurements would suggest. If Tom made his measurements
from 1 MHz to 16 MHz, what do you think the curve would look like?

Freq 1 2 4 8 16 MHz
Delay ___ ___ 3 ___ 16 nS

That looks non-linear to me. How about you?

Definitely nonlinear, just like impedance is very nonlinear as the
frequency passes through any resonance. This is why I am suspicious
of a measurement made at resonance, being extrapolated to non resonant
conditions.