Yuri Blanarovich wrote:
in other words, the highest current point on the structure is at the
inductor.

That's what W8JI calculated in EZnec, does it make sense? Like 2+2 is 4.5? Why
would inductor "suck" the current up? We should then use "those" inductors to
suck the current all the way to the top of the whip - perfect antenna?
Cecil, can you 'splain that?

Again, the current can either stay the same, increase, or decrease through
an inductor depending upon where it is located. Has that statement sunk
in on anyone? If you install a coil 1/8WL up on a 1/2WL vertical, the
current through the coil will *INCREASE*. If you install it in the center,
the current magnitude will be the same in and out of the coil and opposite
in phase. If you install it 1/8WL from the top, the current will decrease
through the coil like it does on a 1/4WL mobile antenna.
--
73, Cecil http://www.qsl.net/w5dxp



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Again, the current can either stay the same, increase, or decrease through
an inductor depending upon where it is located. Has that statement sunk
in on anyone?

Yes,
to be more precise, we are actualy arguing about the case of resonant quarter
wave vertical, as a typical mobile antenna.

Other losses, such as ground conditions, poor contacts, color of eyes are not
considered here.

Yuri

Tell us, Cecil, at steady state at one frequency, can a lumped inductor
(presumably like the experimenter's toroid) tell whether it's at the
base of an antenna or simply in series between a generator and load
impedance?

Yes_____

No______

If you answered "yes", please explain how and why, and how we'd
calculate the current through and voltage across the inductor. If we
moved it an inch up the transmission line from the antenna base, can it
still tell?

If you answered "no", please write us the equations showing just how
much the current should be expected to be different from one end of the
inductor to the other. And where those coulombs are going, that go into
one end and don't come out the other. Going to the fourth dimension as
virtual photons, perhaps?

Roy Lewallen, W7EL

Cecil Moore wrote:
Yuri Blanarovich wrote:

in other words, the highest current point on the structure is at the
inductor.

That's what W8JI calculated in EZnec, does it make sense? Like 2+2 is
4.5? Why
would inductor "suck" the current up? We should then use "those"
inductors to
suck the current all the way to the top of the whip - perfect antenna?
Cecil, can you 'splain that?


Again, the current can either stay the same, increase, or decrease through
an inductor depending upon where it is located. Has that statement sunk
in on anyone? If you install a coil 1/8WL up on a 1/2WL vertical, the
current through the coil will *INCREASE*. If you install it in the center,
the current magnitude will be the same in and out of the coil and opposite
in phase. If you install it 1/8WL from the top, the current will decrease
through the coil like it does on a 1/4WL mobile antenna.

Roy, W7EL addressed several provocative questions to Cecil. Anyone can
comment, so I will.

Roy wrote:
"And where those coulombs are going that go into one end of the inductor
and don`t come out the other."

Coulombs travel back and forth in an inductor and may go actually
nowhere. Their movement in an unshielded inductance may result in
radiation and certainly produces some heat.

The purpose of a loading coil in a short loaded vertical antenna is
often to add to the existing degrees of antenna length to reach a
resonant length of 90-degrees, as shown in Fig 9-22 of ON4UN`s "Low-Band
DXing", and included on Yuri`s web pages.

Fig 9-22 is illustrative. First, a full-size 90-degree vertical is
shown. Current is maximum at the base and zero at the top. This is also
true for what Kraus calls a "normal-mode helical antenna". A normal-mode
helical antenna has its principal radiation at right-angles to the axis
of the helix.

The normal-mode helix is fed from a generator with two terminals. One
terminal feeds the base end of the helix directly. The other generator
terminal feeds the ground end of a capacitance between the ground,
various turns, and the tip end of the helix.

The impedance is only a few ohms at the ground end of the helix and
perhaps several thousand ohms at the tip end of the helix. This means a
lot more amps at the ground end of the helix than at the tip end, though
the power flow through the generator`s terminals is the same in either
terminal.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
The purpose of a loading coil in a short loaded vertical antenna is
often to add to the existing degrees of antenna length to reach a
resonant length of 90-degrees, as shown in Fig 9-22 of ON4UN`s "Low-Band
DXing", and included on Yuri`s web pages.

In order for a current maximum to exist at the feedpoint of a shortened
(less than 1/4WL) vertical, the forward current must undergo a phase
shift of 90 degrees, followed by the 180 degree phase shift from being
reflected by an open circuit, followed by another 90 degree phase shift
in the reflected current wave. An 8 foot whip gives about 11 degrees of
phase shift end to end on 75m for a total of 22 degrees. If the coil
causes no phase shift, where does the other 338 degrees of phase shift
come from?
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:
Richard Harrison wrote:
The purpose of a loading coil in a short loaded vertical antenna is
often to add to the existing degrees of antenna length to reach a
resonant length of 90-degrees, as shown in Fig 9-22 of ON4UN`s "Low-Band
DXing", and included on Yuri`s web pages.

In order for a current maximum to exist at the feedpoint of a shortened
(less than 1/4WL) vertical, the forward current must undergo a phase
shift of 90 degrees, followed by the 180 degree phase shift from being
reflected by an open circuit, followed by another 90 degree phase shift
in the reflected current wave. An 8 foot whip gives about 11 degrees of
phase shift end to end on 75m for a total of 22 degrees. If the coil
causes no phase shift, where does the other 338 degrees of phase shift
come from?

Some people thought I was disagreeing with Richard. I wasn't. I was
agreeing with him and adding another reason why he is right. Incidentally,
the 338 degrees above should have been 158 degrees. I forgot to subtract
the 180 degree current phase reversal at the end of the standing-wave
antenna. Since the coil is the only other thing in the circuit, it
must necessarily contribute that 158 degrees, 79 degrees in each
direction.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:
Tell us, Cecil, at steady state at one frequency, can a lumped inductor
(presumably like the experimenter's toroid) tell whether it's at the
base of an antenna or simply in series between a generator and load
impedance?

This question proves you don't understand the problem. The inductor
cannot tell if it is installed in an antenna or transmission line.

So I will turn the question around: Does a standing wave antenna
have standing waves? Reference _Antenna_Theory- by Balanis, page 17,
section 1.4 Current Distrubution on a Thin Wire Antenna. Is Balanis
correct when he says: "If the diameter of each wire is very small,
the ideal standing wave pattern of the current along the arms of
the (1/2WL) dipole is sinusoidal with a null at the end."

This is after he takes an unterminated transmission line, discusses
standing waves, and then slowly opens up the ends of the transmission
line to create a 1/2WL dipole.

I took Balanis' antenna course at ASU in 1995. I asked a lot of
questions about inductively loaded antennas. The current and
standing wave pattern on each side of a loading coil is NOT the same.
--
73, Cecil http://www.qsl.net/w5dxp



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So, was that a yes or a no? I have trouble with your accent.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

Tell us, Cecil, at steady state at one frequency, can a lumped
inductor (presumably like the experimenter's toroid) tell whether it's
at the base of an antenna or simply in series between a generator and
load impedance?


This question proves you don't understand the problem. The inductor
cannot tell if it is installed in an antenna or transmission line.

So I will turn the question around: Does a standing wave antenna
have standing waves? Reference _Antenna_Theory- by Balanis, page 17,
section 1.4 Current Distrubution on a Thin Wire Antenna. Is Balanis
correct when he says: "If the diameter of each wire is very small,
the ideal standing wave pattern of the current along the arms of
the (1/2WL) dipole is sinusoidal with a null at the end."

This is after he takes an unterminated transmission line, discusses
standing waves, and then slowly opens up the ends of the transmission
line to create a 1/2WL dipole.

I took Balanis' antenna course at ASU in 1995. I asked a lot of
questions about inductively loaded antennas. The current and
standing wave pattern on each side of a loading coil is NOT the same.

Roy Lewallen wrote:

So, was that a yes or a no? I have trouble with your accent.

It's a no. Lumped inductors are not conscious of anything
including their locations.
--
73, Cecil http://www.qsl.net/w5dxp



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Good. And I see from your other response that you understand the question.

So now we have a simple series circuit consisting of a generator, the
loading inductor, and the R + L or C we used to substitute for the
antenna. And your "no" response indicates you've agreed that the voltage
across and current through the inductor are the same as when it was
connected to the antenna.

Now, choose any values you'd like for the generator voltage or current
and the component values, and write the equations showing that the
current into the inductor is different in any way (amplitude or phase)
from the current going out. Or, if that's too taxing, I'll choose some
values for you.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

So, was that a yes or a no? I have trouble with your accent.


It's a no. Lumped inductors are not conscious of anything
including their locations.