Richard Harrison wrote:

Cecil, W5DXP wrote:
"Until someone can explain exactly how a lumped inductor causes a
45-degree phase shift in the current, I`m going to assume that a lumped
inductor is incapable of that feat."

There are base loading coils in shielded boxes which don`t radiate but
do have significant inductance which make too-short antennas seem long
enough for impedance matching purposes.

But the point is, those loading coils in shielded boxes are NOT *lumped
inductors*. We have been told that lumped inductors have zero phase shift.
Apparently, a 45-degree phase shift in the current through a lumped inductor
would violate the rules of usage for lumped inductors.

I have no doubt that real-world inductors provide a phase shift in the
current. My statement was limited entirely to lumped inductors, a purely
imaginary conceptual model. Sorry if that wasn't clear.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

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.

73, Jim AC6XG

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



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

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



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Cecil, W5DXP wrote:
"My statement was limited entirely to lumped inductors, a purely
imaginary conceptual model."

Sorry I didn`t get the picture. An inductor that provides no phase shift
is similar to a capacitor that holds no charge. Inductors and capacitors
store energies in their magnetic and electric fields. Current lags in
the inductor and leads in the capacitor. Pure reactances have a
90-degree phase shift between applied voltage and resulting current by
definition.

An inductor sans phase shift is salt without savor or sugar without
sweetness.

Lumped inductance means coiled in place of straight wire, to me.
Reference to toroidal coils in this thread implied to me an absence of
external field, for which I chose a shielded coil with a straight-axis
for my example.

I agree with Cecil that a 90-degree antenna which includes only a
45-degree length of wire needs another 45-degree phase-shift in its
length to reach the full 90-degrees.

As the coil is in series with a resistance, and the resistance the coil
experiences depends upon its position between drivepoint
(low-resistance) and far end (high resistance) at the end of the
element, the inductance required to produce the same required phase
shift, varies with its position in the element.

Where the resistance is low, so is the required inductance. Where the
resistance is high, so is the required inductance, and it is all for the
same number of degrees that the antenna is short.

Best regards, Richard Harrison, KB5WZI