Jim Kelley wrote:

Cecil Moore wrote:
We have been told that lumped inductors have zero phase shift.

I think the claim is that there is zero current differential in
magnitude across a lumped inductor. It's certainly true of a pure
inductor. Presumably, one in which radiation is not a factor, and for
which the electrical length is short compared to wavelength.

For a lumped inductance, the electrical length is zero. Presumably,
that has a zero effect on the current. Assuming that only the voltage
is affected, the phase relationship between the voltage and current
is blown compared to an unloaded antenna. But the relationship is
somehow (magically?) restored by the time the end of the antenna is
encountered. Exactly how is that relationship restored?
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Jim Kelley wrote:

Cecil Moore wrote:
We have been told that lumped inductors have zero phase shift.

I think the claim is that there is zero current differential in
magnitude across a lumped inductor. It's certainly true of a pure
inductor. Presumably, one in which radiation is not a factor, and for
which the electrical length is short compared to wavelength.

For a lumped inductance, the electrical length is zero. Presumably,
that has a zero effect on the current. Assuming that only the voltage
is affected, the phase relationship between the voltage and current
is blown compared to an unloaded antenna. But the relationship is
somehow (magically?) restored by the time the end of the antenna is
encountered. Exactly how is that relationship restored?

The problem seems to be caused by the assumption that an inductor has no
current lag in an antenna circuit.

In my experience, lumped circuit elements are just a simplified way of
expressing the characteristics of device that has distributed reactances
and resistance. You draw the equivalent circuit as inductors,
capacitors, and resistors in series and shunt where appropriate, and
assign the appropriate values to each. You can do that just as easily
with an antenna as with a transformer. In the case of a loading coil,
perhaps you could say that a portion of the "lumped" inductance of the
antenna is replaced with a coil inductor. From a relative size
standpoint, the inductance of the coil is certainly "lumped" compared
the inductance of the rest of the antenna. But does size matter? :-)
As Richard alluded, an inductor with zero phase shift must have zero
inductance. I think it's safe to assume loading coils cause a phase
shift. But what of the current differential? Seems difficult to
believe that current can go from max to min, and impedance and voltage
go from min to max along the 15" of a 40 meter hamstick whip.

73, Jim AC6XG

Jim Kelley wrote:
Seems difficult to
believe that current can go from max to min, and impedance and voltage
go from min to max along the 15" of a 40 meter hamstick whip.

Not difficult at all for True Believers of Old Wives' Tales
or hams seduced by the steady-state model. :-) Component energy
waves don't matter, don'tcha know? Never mind that standing waves
are probably impossible without forward waves and reverse waves.
--
73, Cecil http://www.qsl.net/w5dxp



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