Michael Tope wrote:
Will the
value of inductive reactance needed to "resonate" my
loaded transmission line vary with the delay and or
form factor of the parallel loading inductors, or will
this value be fixed and equal to the value of inductive
reactance required when I was using the ideal "black
box" inductors?

Hopefully you alll see where I am going with
this. What say, Gents?

Hi Mike, good posting. I admire open, questioning minds. I
just added some information on this subject to my web page.
Although there is some relationship between inductance and
delay, I hardly had to mention inductance at all. The phases
of the forward current and reflected current are changing in
opposite directions. Given any delay at all, the magnitude of
the net current will change through the coil (given a typical
mobile antenna coil). The electrical length of a mobile antenna
loading coil can be approximated by finding the angle whose
cosine is (net top current)/(net bottom current). Note that this
estimate works for loading coils installed in electrical 1/4WL
monopoles or electrical 1/2WL dipoles, not for the general case.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil, W5DXP wrote:
"I hardly had to mention inductance at all."

Imductance equals delay. That`s why inductors are called retardation
coils.

In a resistor, current varies exactly in the same way and at the same
time as the applied voltage. Volts and amps are in-phase.

In an inductor, current is delayed and builds from the time that voltage
appears across the inductor. In a lossless (pure) inductance, current
lags the applied a-c voltage by 90-degrees. When the voltage is maximum,
current is zero, and when the voltage is zero, current is maximum.

90-degrees represents some fraction of a second, depending on cycles per
second as 90-degrees is the time required for 1/4-cycle. The higher the
frequency, the shorter the time represented by 90-degrees.

Loss in an inductance makes an impedance composed of inductive reactance
and resistance. As current is delayed in reactance by 90-degrees, but is
in-synch in a resistance,
Pythagoras gives us the total impedance, and the phase angle of the
resultant impedance is an "operational vector", not a "field vector".
The angle of current in the impure inductance which is made with the
applied voltage is easily determined with trigonometry or graphical
methods. An operational vector is also called a phasor. Delay can vary
from 0 in a pure resistance to 90-degrees in a purely reactive circuit.

Inductance makes current lag by 90-degrees. Capacitance makes current
lead by 90-degrees.

Broadcasters use a T-network called a 90-degree phase shifter. All three
reactances have the same impedance as the input and output impedance.

For example, two 50-ohm reactance coils are connected in series in the
signal path. A 50-ohm capacitive reactance is connected between the
junction of the two coils and the other side of the circuit (ground).

One of the coils cancels the capacitive reactance, leaving a pure
inductive reactance of 50-ohms in series with the circuit to cause a
90-degree phase lag. Often ganged variable inductors are used in the
90-degree phase shifter to produce the exact delay required and this has
almost no effect, less than 1%, on output current magnitude from the
phase shifter over a plus or minus 15-degree phase adjustment range.
It`s simple trigonometry.

Best regards, Richard Harrison, KB5WZI